Light-Emitting Element, Light-Emitting Device, Electronic Device, and Lighting Device

ABSTRACT

To provide a novel light-emitting device, a light-emitting device that emits light of a plurality of colors includes a first light-emitting element and a second light-emitting element. The first light-emitting element includes a first lower electrode, a first light-emitting layer over the first lower electrode, a second light-emitting layer over the first light-emitting layer, and an upper electrode over the second light-emitting layer. The second light-emitting element includes a second lower electrode, the first light-emitting layer over the second lower electrode, the second light-emitting layer over the first light-emitting layer, and the upper electrode over the second light-emitting layer. An emission spectrum of the first light-emitting layer peaks at a longer wavelength than an emission spectrum of the second light-emitting layer. A distance between the first lower electrode and the first light-emitting layer is shorter than a distance between the second lower electrode and the first light-emitting layer.

This application is a divisional of copending U.S. application Ser. No.14/920,335, filed on Oct. 22, 2015 which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

One embodiment of the present invention relates to a light-emittingelement in which a light-emitting layer capable of providing lightemission by application of an electric field is provided between a pairof electrodes, and also relates to a light-emitting device, anelectronic device, and a lighting device each including such alight-emitting element.

Note that one embodiment of the present invention is not limited to theabove technical field. The technical field of one embodiment of theinvention disclosed in this specification and the like relates to anobject, a method, or a manufacturing method. In addition, one embodimentof the present invention relates to a process, a machine, manufacture,or a composition of matter. Specifically, examples of the technicalfield of one embodiment of the present invention disclosed in thisspecification include a semiconductor device, a display device, a liquidcrystal display device, a light-emitting device, a lighting device, apower storage device, a storage device, a driving method thereof, and amanufacturing method thereof.

2. Description of the Related Art

In recent years, research and development have been extensivelyconducted on light-emitting elements utilizing electroluminescence (EL).In a basic structure of these light-emitting elements, a layercontaining a light-emitting substance is provided between a pair ofelectrodes. By application of a voltage to this element, light emittedfrom the light-emitting substance can be obtained.

Since the above light-emitting element is a self-luminous type, alight-emitting device using this light-emitting element has advantagessuch as high visibility, no necessity of a backlight, and low powerconsumption. The light-emitting device using the light-emitting elementalso has advantages in that it can be manufactured to be thin andlightweight and has high response speed.

In order to improve the extraction efficiency of light from alight-emitting element, a method has been proposed, in which a microoptical resonator (microcavity) structure utilizing a resonant effect oflight between a pair of electrodes is used to increase the intensity oflight having a specific wavelength (e.g., see Patent Document 1).

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2012-182127

SUMMARY OF THE INVENTION

When a metal film with high reflectance (e.g., a metal film containingsilver) is used as one of a pair of electrodes in a micro opticalresonator structure (hereinafter referred to as a microcavity structure)utilizing a resonant effect of light between the pair of electrodes,light might be scattered or absorbed in the vicinity of a surface of themetal film with high reflectance under the influence of surface plasmonresonance (SPR), resulting in lower light extraction efficiency.

In view of the above problems, an object of one embodiment of thepresent invention is to provide a novel light-emitting device. Anotherobject is to provide a novel light-emitting device with high emissionefficiency and low power consumption. Another object is to provide amethod for manufacturing the novel light-emitting device.

Note that the description of the above objects does not disturb theexistence of other objects. In one embodiment of the present invention,there is no need to achieve all the objects. Other objects will beapparent and can be derived from the description of the specificationand the like.

One embodiment of the present invention is a light-emitting device thatemits light of a plurality of colors. The light-emitting device includesa first light-emitting element and a second light-emitting element. Thefirst light-emitting element includes a first lower electrode, a firstlight-emitting layer over the first lower electrode, a secondlight-emitting layer over the first light-emitting layer, and an upperelectrode over the second light-emitting layer. The secondlight-emitting element includes a second lower electrode, the firstlight-emitting layer over the second lower electrode, the secondlight-emitting layer over the first light-emitting layer, and the upperelectrode over the second light-emitting layer. An emission spectrum ofthe first light-emitting layer peaks at a longer wavelength than anemission spectrum of the second light-emitting layer. A distance betweenthe first lower electrode and the first light-emitting layer is shorterthan a distance between the second lower electrode and the firstlight-emitting layer.

Another embodiment of the present invention is a light-emitting devicethat emits light of a plurality of colors. The light-emitting deviceincludes a first light-emitting element and a second light-emittingelement. The first light-emitting element includes a first lowerelectrode, a first light-emitting layer over the first lower electrode,a second light-emitting layer over the first light-emitting layer, andan upper electrode over the second light-emitting layer. The secondlight-emitting element includes a second lower electrode, the firstlight-emitting layer over the second lower electrode, the secondlight-emitting layer over the first light-emitting layer, and the upperelectrode over the second light-emitting layer. A spectrum of lightemitted from the first light-emitting layer has a peak of any one ofgreen, yellow green, yellow, orange, and red. A spectrum of lightemitted from the second light-emitting layer has a peak of any one ofviolet, blue, and blue green. A distance between the first lowerelectrode and the first light-emitting layer is shorter than a distancebetween the second lower electrode and the first light-emitting layer.

In either of the above embodiments, it is preferable that light emittedfrom the first light-emitting element have at least one peak in a bluewavelength range and light emitted from the second light-emittingelement have at least one peak in a yellow wavelength range. Moreover,in either of the above embodiments, it is preferable that an opticalpath length between the first lower electrode and the secondlight-emitting layer be approximately 3λ_(B)/4 (λ_(B) represents awavelength of blue light) and an optical path length between the secondlower electrode and the first light-emitting layer be approximately3λ_(Y)/4 (λ_(Y) represents a wavelength of yellow light). Note that inthis specification and the like, approximately 3λ_(X)/4 (λ_(X)represents any one of λ_(R), λ_(G), λ_(B), and λ_(Y)) is within therange of ±20 nm of 3λ_(X)/4, preferably ±10 nm of 3λ_(X)/4.

In either of the above embodiments, the first lower electrode and thesecond lower electrode each preferably include silver.

Another embodiment of the present invention is a light-emitting devicethat emits light of a plurality of colors. The light-emitting deviceincludes a first light-emitting element, a second light-emittingelement, and a third light-emitting element. The first light-emittingelement includes a first lower electrode, a first transparent conductivelayer over the first lower electrode, a first light-emitting layer overthe first transparent conductive layer, a charge-generation layer overthe first light-emitting layer, a second light-emitting layer over thecharge-generation layer, and an upper electrode over the secondlight-emitting layer. The second light-emitting element includes asecond lower electrode, a second transparent conductive layer over thesecond lower electrode, the first light-emitting layer over the secondtransparent conductive layer, the charge-generation layer over the firstlight-emitting layer, the second light-emitting layer over thecharge-generation layer, and the upper electrode over the secondlight-emitting layer. The third light-emitting element includes a thirdlower electrode, a third transparent conductive layer over the thirdlower electrode, the first light-emitting layer over the thirdtransparent conductive layer, the charge-generation layer over the firstlight-emitting layer, the second light-emitting layer over thecharge-generation layer, and the upper electrode over the secondlight-emitting layer. Light emitted from the first light-emittingelement has at least one peak in a wavelength range of greater than orequal to 400 nm and less than 480 nm. Light emitted from the secondlight-emitting element has at least one peak in a wavelength range ofgreater than or equal to 480 nm and less than 600 nm. Light emitted fromthe third light-emitting element has at least one peak in a wavelengthrange of greater than or equal to 600 nm and less than or equal to 740nm.

Another embodiment of the present invention is a light-emitting devicethat emits light of a plurality of colors. The light-emitting deviceincludes a first light-emitting element, a second light-emittingelement, a third light-emitting element, and a fourth light-emittingelement. The first light-emitting element includes a first lowerelectrode, a first transparent conductive layer over the first lowerelectrode, a first light-emitting layer over the first transparentconductive layer, a charge-generation layer over the firstlight-emitting layer, a second light-emitting layer over thecharge-generation layer, and an upper electrode over the secondlight-emitting layer. The second light-emitting element includes asecond lower electrode, a second transparent conductive layer over thesecond lower electrode, the first light-emitting layer over the secondtransparent conductive layer, the charge-generation layer over the firstlight-emitting layer, the second light-emitting layer over thecharge-generation layer, and the upper electrode over the secondlight-emitting layer. The third light-emitting element includes a thirdlower electrode, a third transparent conductive layer over the thirdlower electrode, the first light-emitting layer over the thirdtransparent conductive layer, the charge-generation layer over the firstlight-emitting layer, the second light-emitting layer over thecharge-generation layer, and the upper electrode over the secondlight-emitting layer. The fourth light-emitting element includes afourth lower electrode, a fourth transparent conductive layer over thefourth lower electrode, the first light-emitting layer over the fourthtransparent conductive layer, the charge-generation layer over the firstlight-emitting layer, the second light-emitting layer over thecharge-generation layer, and the upper electrode over the secondlight-emitting layer. Light emitted from the first light-emittingelement has at least one peak in a wavelength range of greater than orequal to 400 nm and less than 480 nm. Light emitted from the secondlight-emitting element has at least one peak in a wavelength range ofgreater than or equal to 550 nm and less than 600 nm. Light emitted fromthe third light-emitting element has at least one peak in a wavelengthrange of greater than or equal to 600 nm and less than or equal to 740nm. Light emitted from the fourth light-emitting element has at leastone peak in a wavelength range of greater than or equal to 480 nm andless than 550 nm.

In any of the above embodiments, it is preferable that the firstlight-emitting layer includes a phosphorescent material and the secondlight-emitting layer includes a fluorescent material.

One embodiment of the present invention includes, in its scope, anelectronic device including the light-emitting device in each of theabove embodiments and having a housing or a touch sensor or a lightingdevice including the light-emitting device in each of the aboveembodiments and a housing. Note that a light-emitting device in thisspecification refers to an image display device or a light source(including a lighting device). Furthermore, a light-emitting devicemight include, in its category, all of a module in which alight-emitting device is connected to a connector such as a flexibleprinted circuit (FPC) or a tape carrier package (TCP), a module in whicha printed wiring board is provided on the tip of a TCP, and a module inwhich an integrated circuit (IC) is directly mounted on a light-emittingelement by a chip on glass (COG) method.

According to one embodiment of the present invention, a novellight-emitting device can be provided. According to another embodimentof the present invention, a novel light-emitting device with highemission efficiency and low power consumption can be provided. Accordingto another embodiment of the present invention, a method formanufacturing the novel light-emitting device can be provided.

Note that the description of these effects does not disturb theexistence of other effects. One embodiment of the present invention doesnot necessarily achieve all the effects listed above. Other effects willbe apparent and can be derived from the description of thespecification, the drawings, the claims, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a light-emitting device.

FIG. 2 is a cross-sectional view illustrating a light-emitting device.

FIG. 3 is a cross-sectional view illustrating a light-emitting device.

FIG. 4 is a cross-sectional view illustrating a light-emitting device.

FIG. 5 is a cross-sectional view illustrating a light-emitting device.

FIG. 6 is a cross-sectional view illustrating a light-emitting device.

FIG. 7 is a cross-sectional view illustrating a light-emitting device.

FIG. 8 is a cross-sectional view illustrating a light-emitting device.

FIG. 9 is a cross-sectional view illustrating a light-emitting device.

FIG. 10 is a cross-sectional view illustrating a light-emitting device.

FIG. 11 is a cross-sectional view illustrating a light-emitting device.

FIG. 12 is a cross-sectional view illustrating a light-emitting device.

FIG. 13 is a cross-sectional view illustrating a transistor.

FIGS. 14A and 14B are cross-sectional views illustrating a method formanufacturing a light-emitting device.

FIGS. 15A and 15B are cross-sectional views illustrating a method formanufacturing the light-emitting device.

FIGS. 16A and 16B are cross-sectional views illustrating a method formanufacturing the light-emitting device.

FIGS. 17A and 17B are a block diagram and a circuit diagram illustratinga display device.

FIGS. 18A and 18B are each a circuit diagram illustrating a pixelcircuit of a display device.

FIGS. 19A and 19B are each a circuit diagram illustrating a pixelcircuit of a display device.

FIGS. 20A and 20B are perspective views of an example of a touch panel.

FIGS. 21A to 21C are cross-sectional views of examples of a displaypanel and a touch sensor.

FIGS. 22A and 22B are each a cross-sectional view of an example of atouch panel.

FIGS. 23A and 23B are a block diagram and a timing chart of a touchsensor.

FIG. 24 is a circuit diagram of a touch sensor.

FIG. 25 is a perspective view of a display module.

FIGS. 26A to 26G illustrate electronic devices.

FIGS. 27A to 27C are a perspective view and cross-sectional viewsillustrating a light-emitting device.

FIGS. 28A to 28D are cross-sectional views illustrating a light-emittingdevice.

FIGS. 29A to 29C illustrate a lighting device and an electronic device.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the drawings. Note that one embodiment of the presentinvention is not limited to the following description, and the modes anddetails thereof can be modified in various ways without departing fromthe spirit and scope of the present invention. Accordingly, oneembodiment of the present invention should not be interpreted as beinglimited to the content of the embodiments below.

Note that the position, the size, the range, or the like of eachstructure illustrated in drawings and the like is not accuratelyrepresented in some cases for easy understanding. Therefore, oneembodiment of the disclosed invention is not necessarily limited to theposition, the size, the range, or the like disclosed in the drawings andthe like.

The ordinal numbers such as “first” and “second” in this specificationand the like are used for convenience and do not denote the order ofsteps or the stacking order of layers. Therefore, for example,description can be made even when “first” is replaced with “second” or“third”, as appropriate. In addition, the ordinal numbers in thisspecification and the like are not necessarily the same as those whichspecify one embodiment of the present invention.

In order to describe structures of the invention with reference to thedrawings in this specification and the like, the same reference numeralsare used in common for the same portions in different drawings.

In this specification and the like, the wavelength range of blue lightis greater than or equal to 400 nm and less than 480 nm, the wavelengthrange of green light is greater than or equal to 480 nm and less than550 nm, the wavelength range of yellow light is greater than or equal to550 nm and less than 600 nm, and the wavelength range of red light isgreater than or equal to 600 nm and less than or equal to 740 nm.

In this specification and the like, a transparent conductive layertransmits visible light and has conductivity. Examples of thetransparent conductive layer include an oxide conductor film typified byan indium tin oxide (ITO) film, an oxide semiconductor film, an organicconductive film containing an organic substance, and the like. Examplesof the organic conductive film containing an organic substance include afilm containing a composite material in which an organic compound and anelectron donor (donor) are mixed, a film containing a composite materialin which an organic compound and an electron acceptor (acceptor) aremixed, and the like. The resistivity of the transparent conductive layeris preferably lower than or equal to 1×10⁵ Ω·cm and further preferablylower than or equal to 1×10⁴ Ω·cm.

In this specification and the like, the terms “film” and “layer” can beinterchanged with each other. For example, the term “conductive layer”can be changed into the term “conductive film” in some cases. Also, theterm “insulating film” can be changed into the term “insulating layer”in some cases.

Embodiment 1

In this embodiment, a light-emitting device of one embodiment of thepresent invention and a method for manufacturing the light-emittingdevice will be described below with reference to FIGS. 1 to 13, FIGS.14A and 14B, FIGS. 15A and 15B, and FIGS. 16A and 16B.

Structural Example 1 of Light-Emitting Device

FIG. 1 is a cross-sectional view illustrating an example of alight-emitting device of one embodiment of the present invention. Alight-emitting device 100 illustrated in FIG. 1 includes a firstlight-emitting element 101B and a second light-emitting element 101Y.The first light-emitting element 101B includes a first lower electrode104B, a first light-emitting layer 108 over the first lower electrode104B, a second light-emitting layer 110 over the first light-emittinglayer 108, and an upper electrode 112 over the second light-emittinglayer 110. The second light-emitting element 101Y includes a secondlower electrode 104Y, the first light-emitting layer 108 over the secondlower electrode 104Y, the second light-emitting layer 110 over the firstlight-emitting layer 108, and the upper electrode 112 over the secondlight-emitting layer 110. The emission spectrum of the firstlight-emitting layer 108 peaks at a longer wavelength than that of thesecond light-emitting layer 110, and the distance between the firstlower electrode 104B and the first light-emitting layer 108 is shorterthan the distance between the second lower electrode 104Y and the firstlight-emitting layer 108.

The first light-emitting element 101B further includes a firsttransparent conductive layer 106B, a hole-injection layer 131, ahole-transport layer 132, an electron-transport layer 133,charge-generation layers 141 a and 141 b, a hole-injection layer 134, ahole-transport layer 135, and an electron-transport layer 136. Note thatin the first light-emitting element 101B, the first transparentconductive layer 106B, the hole-injection layer 131, and thehole-transport layer 132 are provided between the first lower electrode104B and the first light-emitting layer 108.

The second light-emitting element 101Y further includes a secondtransparent conductive layer 106Y, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thecharge-generation layers 141 a and 141 b, the hole-injection layer 134,the hole-transport layer 135, and the electron-transport layer 136. Notethat in the second light-emitting element 101Y, the second transparentconductive layer 106Y, the hole-injection layer 131, and thehole-transport layer 132 are provided between the second lower electrode104Y and the first light-emitting layer 108.

In each of the first light-emitting element 101B and the secondlight-emitting element 101Y, the electron-transport layer 133, thecharge-generation layers 141 a and 141 b, the hole-injection layer 134,and the hole-transport layer 135 are provided between the firstlight-emitting layer 108 and the second light-emitting layer 110. Theelectron-transport layer 136 is provided between the secondlight-emitting layer 110 and the upper electrode 112.

A spectrum of light emitted from the first light-emitting layer 108 hasa peak of any one of green, yellow green, yellow, orange, and red. Inother words, the first light-emitting layer 108 includes alight-emitting substance that emits light of any one of green, yellowgreen, yellow, orange, and red. A spectrum of light emitted from thesecond light-emitting layer 110 has a peak of any one of violet, blue,and blue green. In other words, the second light-emitting layer 110includes a light-emitting substance that emits light of any one ofviolet, blue, and blue green.

For example, the first light-emitting layer 108 can be formed using aphosphorescent material emitting yellow light as a light-emittingsubstance, and the second light-emitting layer 110 can be formed using afluorescent material emitting blue light as a light-emitting substance.

In FIG. 1, blue light (B) and yellow light (Y) emitted from theirrespective light-emitting elements are schematically denoted by arrowsof dashed lines. The light-emitting device 100 illustrated in FIG. 1 hasa top-emission structure in which light emitted from light-emittingelements is extracted to the side opposite to the substrate 102 sidewhere the light-emitting elements are formed. However, one embodiment ofthe present invention is not limited thereto and may have abottom-emission structure in which light emitted from light-emittingelements is extracted to the substrate side where the light-emittingelements are formed, or a dual-emission structure in which light emittedfrom light-emitting elements is extracted in both top and bottomdirections of the substrate 102 where the light-emitting elements areformed. FIG. 6 illustrates an example of the bottom-emissionlight-emitting device. FIG. 6 is a cross-sectional view in the casewhere the light-emitting device 100 illustrated in FIG. 1 is abottom-emission light-emitting device.

Note that in an example shown in FIG. 1, the hole-injection layer 131,the hole-transport layer 132, the first light-emitting layer 108, theelectron-transport layer 133, the charge-generation layers 141 a and 141b, the hole-injection layer 134, the hole-transport layer 135, thesecond light-emitting layer 110, and the electron-transport layer 136are each divided to form the first light-emitting element 101B and thesecond light-emitting element 101Y; however, they can also be usedwithout being divided. Therefore, in the second light-emitting element101Y, the hole-injection layer 131, the hole-transport layer 132, thefirst light-emitting layer 108, the electron-transport layer 133, thecharge-generation layers 141 a and 141 b, the hole-injection layer 134,the hole-transport layer 135, the second light-emitting layer 110, andthe electron-transport layer 136 are represented by the same hatchingpatterns as in the first light-emitting element 101B and not especiallydenoted by reference numerals.

The first light-emitting element 101B and the second light-emittingelement 101Y each have a microcavity structure. The microcavitystructure of each light-emitting element is described below.

Light emitted from the first light-emitting layer 108 and the secondlight-emitting layer 110 resonates between two pairs of electrodes (apair of the first lower electrode 104B and the upper electrode 112, anda pair of the second lower electrode 104Y and the upper electrode 112).In the light-emitting device 100, the thickness of each of the firsttransparent conductive layer 106B and the second transparent conductivelayer 106Y in the light-emitting elements is adjusted so that desiredwavelengths of light emitted from the first light-emitting layer 108 andlight emitted from the second light-emitting layer 110 can beintensified.

Specifically, the thickness of the first transparent conductive layer106B is adjusted so that the optical path length between the first lowerelectrode 104B and the upper electrode 112 can be mλ_(B)/2 (m is anatural number and λ_(B) is a wavelength of blue light). Note that inFIG. 1, the thickness of the first transparent conductive layer 106B isadjusted so that the optical path length between the first lowerelectrode 104B and the upper electrode 112 can be λ_(B). The thicknessof the second transparent conductive layer 106Y is adjusted so that theoptical path length between the second lower electrode 104Y and theupper electrode 112 can be mλ_(Y)/2 (in is a natural number and λ_(Y) isa wavelength of yellow light). Note that in FIG. 1, the thickness of thesecond transparent conductive layer 106Y is adjusted so that the opticalpath length between the second lower electrode 104Y and the upperelectrode 112 can be 3λ_(Y)/2.

Note that in the light-emitting device 100 illustrated in FIG. 1, thestructure is described as an example in which the distance between eachof the lower electrodes and the first light-emitting layer 108 isdifferentiated by the thickness of the transparent conductive layers(the first transparent conductive layer 106B and the second transparentconductive layer 106Y). However, without limitation thereto, thedistance between the lower electrode and the first light-emitting layer108 may be differentiated by the thickness of one or both of thehole-injection layer 131 and the hole-transport layer 132. However, asshown in the light-emitting device 100 illustrated in FIG. 1, it ispreferable to differentiate the distance between the lower electrode andthe first light-emitting layer 108 by changing the thickness of thetransparent conductive layer because the hole-injection layer 131 andthe hole-transport layer 132 can be shared by the first light-emittingelement 101B and the second light-emitting element 101Y.

By adjusting the thickness of the first transparent conductive layer106B, the optical path length between the first lower electrode 104B andthe second light-emitting layer 110 can be set to 3λ_(B)/4 (λ_(B)represents a wavelength of blue light). Furthermore, by adjusting thethickness of the first transparent conductive layer 106B, the opticalpath length between the hole-transport layer 135 and the upper electrode112 can be set to λ_(B)/4. Note that here, the optical path lengthbetween the hole-transport layer 135 and the upper electrode 112 is setto λ_(B)/4 because a light-emitting region in the second light-emittinglayer 110 is located in the vicinity of the interface between thehole-transport layer 135 and the second light-emitting layer 110;however, to be exact, the optical path length between the light-emittingregion in the second light-emitting layer 110 and the upper electrode112 is preferred to be set to λ_(B)/4.

For example, in the case where the distance between the first lowerelectrode 104B and the second light-emitting layer 110 is short,specifically, in the case where the optical path length between thefirst lower electrode 104B and the second light-emitting layer 110 isλ_(B)/4, in some cases, light emitted from the second light-emittinglayer 110 attenuates owing to scattering or absorption in the vicinityof the surface of the first lower electrode 104B, resulting in adecrease in light extraction efficiency. However, in the light-emittingdevice 100, the optical path length between the first lower electrode104B and the second light-emitting layer 110 is set to 3λ_(B)/4, wherebyscattering or absorption of light in the vicinity of the first lowerelectrode 104B can be suppressed and thus the efficiency of extractionof light from the second light-emitting layer 110 can be improved.Accordingly, in the first light-emitting element 101B, blue light can beefficiently extracted from the light-emitting substance included in thesecond light-emitting layer 110.

By adjusting the thickness of the second transparent conductive layer106Y, the optical path length between the second lower electrode 104Yand the first light-emitting layer 108 can be set to 3λ_(Y)/4 (λ_(Y)represents a wavelength of yellow light). Furthermore, by adjusting thethickness of the second transparent conductive layer 106Y, the opticalpath length between the hole-transport layer 132 and the upper electrode112 can be set to 3λ_(Y)/4. Note that here, the optical path lengthbetween the hole-transport layer 132 and the upper electrode 112 is setto 3λ_(Y)/4 because a light-emitting region in the first light-emittinglayer 108 is located in the vicinity of the interface between thehole-transport layer 132 and the first light-emitting layer 108;however, to be exact, the optical path length between the light-emittingregion in the first light-emitting layer 108 and the upper electrode 112is preferred to be set to 3λ_(Y)/4.

For example, in the case where the distance between the second lowerelectrode 104Y and the first light-emitting layer 108 is short,specifically, in the case where the optical path length between thesecond lower electrode 104Y and the first light-emitting layer 108 isλ_(Y)/4, in some cases, light emitted from the first light-emittinglayer 108 attenuates owing to scattering or absorption in the vicinityof the surface of the second lower electrode 104Y, resulting in adecrease in light extraction efficiency. However, in the light-emittingdevice 100, the optical path length between the second lower electrode104Y and the first light-emitting layer 108 is set to 3λ_(Y)/4, wherebyscattering or absorption of light in the vicinity of the second lowerelectrode 104Y can be suppressed and thus the efficiency of extractionof light from the first light-emitting layer 108 can be improved.Accordingly, in the second light-emitting element 101Y, yellow light canbe efficiently extracted from the light-emitting substance included inthe first light-emitting layer 108.

In some cases, there is difficulty in satisfying 3λ_(B)/4 as the opticalpath length between the first lower electrode 104B and the secondlight-emitting layer 110 in the first light-emitting element 101B andsatisfying λ_(Y)/4 as the optical path length between the second lowerelectrode 104Y and the first light-emitting layer 108 in the secondlight-emitting element 101Y because the hole-injection layer 131, thehole-transport layer 132, the first light-emitting layer 108, theelectron-transport layer 133, the charge-generation layers 141 a and 141b, the hole-injection layer 134, the hole-transport layer 135, thesecond light-emitting layer 110, and the electron-transport layer 136are shared by the first light-emitting element 101B and the secondlight-emitting element 101Y. For example, in the case where the opticalpath length between a pair of electrodes in the first light-emittingelement 101B is set to λ_(B), the total thickness of the secondtransparent conductive layer 106Y, the hole-injection layer 131, and thehole-transport layer 132 in the second light-emitting element 101Y needsto be made small (e.g., approximately 20 nm). However, since the opticalpath length between the second lower electrode 104Y and the firstlight-emitting layer 108 is set to 3λ_(Y)/4 in the light-emitting deviceof one embodiment of the present invention, the total thickness of thesecond transparent conductive layer 106Y, the hole-injection layer 131,and the hole-transport layer 132 in the second light-emitting element101Y can be made large.

Furthermore, the optical path length between the first lower electrode104B and the second light-emitting layer 110 is, .to be exact, theoptical path length between a reflective region in the first lowerelectrode 104B and a light-emitting region in the second light-emittinglayer 110. However, it is difficult to precisely determine the positionsof the reflection region in the first lower electrode 104B and thelight-emitting region in the second light-emitting layer 110; therefore,it is assumed that the above effect can be sufficiently obtainedwherever the reflection region and the light-emitting region may be setin the first lower electrode 104B and the second light-emitting layer110, respectively. The same applies to the optical path length betweenthe second lower electrode 104Y and the first light-emitting layer 108.

By adjusting the above-described optical path lengths, the distancebetween the first lower electrode 104B and the first light-emittinglayer 108 can be made shorter than the distance between the second lowerelectrode 104Y and the first light-emitting layer 108.

The first lower electrode 104B and the second lower electrode 104Y areeach formed using a conductive material having a property of reflectingvisible light. For example, a material containing silver may be used asthe conductive material. When the first lower electrode 104B and thesecond lower electrode 104Y are each formed using a material containingsilver, the reflectance can be increased and the emission efficiency ofeach light-emitting element can be increased. For example, a conductivefilm containing silver is formed and separated into an island-shape; inthis way, the first lower electrode 104B and the second lower electrode104Y can be formed. The first lower electrode 104B and the second lowerelectrode 104Y are preferably formed through a step of processing thesame conductive film, because the manufacturing cost can be reduced.

As described above, in the light-emitting device 100 illustrated in FIG.1, in the first light-emitting element 101B, light (e.g., blue light)emitted from the second light-emitting layer 110 is adjusted to beintensified; and in the second light-emitting element 101Y, light (e.g.,yellow light) emitted from the first light-emitting layer 108 isadjusted to be intensified. White light can be obtained by combininglight emitted from the first light-emitting element 101B and lightemitted from the second light-emitting element 101Y.

As described above, in the light-emitting device 100 illustrated in FIG.1, the optical path length between each of the lower electrodes (thefirst lower electrode 104B and the second lower electrode 104Y) and theupper electrode 112 of each light-emitting element is adjusted, wherebyscattering or absorption of light in the vicinity of the lower electrodecan be suppressed and thus high light extraction efficiency can beachieved. Therefore, a novel light-emitting device with high emissionefficiency and low power consumption can be provided.

Structural Example 2 of Light-Emitting Device

Next, a structural example different from the light-emitting device 100illustrated in FIG. 1 is described below with reference to FIG. 2.

FIG. 2 is a cross-sectional view illustrating an example of alight-emitting device of one embodiment of the present invention. InFIG. 2, a portion having a function similar to that in FIG. 1 isrepresented by the same hatch pattern as in FIG. 1 and not especiallydenoted by a reference numeral in some cases. In addition, commonreference numerals are used for portions having similar functions, and adetailed description of the portions is omitted in some cases.

The light-emitting device 100 illustrated in FIG. 2 includes the firstlight-emitting element 101B, a second light-emitting element 101G, and athird light-emitting element 101R. The first light-emitting element 101Bincludes the first lower electrode 104B, the first transparentconductive layer 106B over the first lower electrode 104B, the firstlight-emitting layer 108 over the first transparent conductive layer106B, the charge-generation layers 141 a and 141 b over the firstlight-emitting layer 108, the second light-emitting layer 110 over thecharge-generation layers 141 a and 141 b, and the upper electrode 112over the second light-emitting layer 110. The second light-emittingelement 101G includes a second lower electrode 104G, a secondtransparent conductive layer 106G over the second lower electrode 104G,the first light-emitting layer 108 over the second transparentconductive layer 106G, the charge-generation layers 141 a and 141 b overthe first light-emitting layer 108, the second light-emitting layer 110over the charge-generation layers 141 a and 141 b, and the upperelectrode 112 over the second light-emitting layer 110. The thirdlight-emitting element 101R includes a third lower electrode 104R, athird transparent conductive layer 106R over the third lower electrode104R, the first light-emitting layer 108 over the third transparentconductive layer 106R, the charge-generation layers 141 a and 141 b overthe first light-emitting layer 108, the second light-emitting layer 110over the charge-generation layers 141 a and 141 b, and the upperelectrode 112 over the second light-emitting layer 110.

The first light-emitting element 101B further includes the firsttransparent conductive layer 106B, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the first light-emittingelement 101B, the first transparent conductive layer 106B, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the first lower electrode 104B and the first light-emittinglayer 108.

The second light-emitting element 101G further includes the secondtransparent conductive layer 106G, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the second light-emittingelement 101G, the second transparent conductive layer 106G, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the second lower electrode 104G and the first light-emittinglayer 108.

The third light-emitting element 101R further includes the thirdtransparent conductive layer 106R, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the third light-emittingelement 101R, the third transparent conductive layer 106R, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the third lower electrode 104R and the first light-emittinglayer 108.

In each of the first light-emitting element 101B, the secondlight-emitting element 101G, and the third light-emitting element 101R,the electron-transport layer 133, the charge-generation layers 141 a and141 b, the hole-injection layer 134, and the hole-transport layer 135are provided between the first light-emitting layer 108 and the secondlight-emitting layer 110. The electron-transport layer 136 is providedbetween the second light-emitting layer 110 and the upper electrode 112.

Light emitted from the first light-emitting element 101B has at leastone peak in a wavelength range of greater than or equal to 400 nm andless than 480 nm, light emitted from the second light-emitting element101G has at least one peak in a wavelength range of greater than orequal to 480 nm and less than 600 nm, and light emitted from the thirdlight-emitting element 101R has at least one peak in a wavelength rangeof greater than or equal to 600 nm and less than or equal to 740 nm.Note that it is preferable that light emitted from the secondlight-emitting element 101G is in a wavelength range of greater than orequal to 480 nm and less than 550 nm.

Light emitted from the first light-emitting layer 108 and the secondlight-emitting layer 110 resonates between three pairs of electrodes (apair of the first lower electrode 104B and the upper electrode 112, apair of the second lower electrode 104G and the upper electrode 112, anda pair of the third lower electrode 104R and the upper electrode 112).In the light-emitting device 100 illustrated in FIG. 2, the thickness ofeach of the first transparent conductive layer 106B, the secondtransparent conductive layer 106G, and the third transparent conductivelayer 106R in the light-emitting elements is adjusted so that desiredwavelengths of light emitted from the first light-emitting layer 108 andlight emitted from the second light-emitting layer 110 can beintensified.

Specifically, the thickness of the first transparent conductive layer106B is adjusted so that the optical path length between the first lowerelectrode 104B and the upper electrode 112 can be mλ_(B)/2 (in is anatural number and λ_(B) is a wavelength of blue light). Note that inFIG. 2, the thickness of the first transparent conductive layer 106B isadjusted so that the optical path length between the first lowerelectrode 104B and the upper electrode 112 can be λ_(B). The thicknessof the second transparent conductive layer 106G is adjusted so that theoptical path length between the second lower electrode 104G and theupper electrode 112 can be mλ_(G)/2 (in is a natural number and λ_(G) isa wavelength of green light). Note that in FIG. 2, the thickness of thesecond transparent conductive layer 106G is adjusted so that the opticalpath length between the second lower electrode 104G and the upperelectrode 112 can be 3λ_(G)/2. The thickness of the third transparentconductive layer 106R is adjusted so that the optical path lengthbetween the third lower electrode 104R and the upper electrode 112 canbe mλ_(R)/2 (m is a natural number and λ_(R) is a wavelength of greenlight). Note that in FIG. 2, the thickness of the third transparentconductive layer 106R is adjusted so that the optical path lengthbetween the third lower electrode 104R and the upper electrode 112 canbe 3λ_(R)/2.

Note that the optical path length between the third lower electrode 104Rand the upper electrode 112 is not limited to the above-describedoptical path lengths. For example, the optical path length in FIG. 3 canbe obtained by adjusting the thickness of the third transparentconductive layer 106R. FIG. 3 is a cross-sectional view illustrating anexample of a light-emitting device of one embodiment of the presentinvention.

The light-emitting device 100 illustrated in FIG. 3 is the same as thelight-emitting device 100 illustrated in FIG. 2 in the structures of thefirst light-emitting element 101B and the second light-emitting element101G and is different therefrom in the optical path length between thethird lower electrode 104R and the first light-emitting layer 108 in thethird light-emitting element 101R. Specifically, by adjusting thethickness of the third transparent conductive layer 106R, the opticalpath length between the third lower electrode 104R and the firstlight-emitting layer 108 can be set to approximately &_(R)/4 (X_(R)represents a wavelength of red light). By adjusting the thickness of thethird transparent conductive layer 106R, the optical path length betweenthe third lower electrode 104R and the upper electrode 112 can be set toapproximately λ_(R).

Structural Example 3 of Light-Emitting Device

Next, a structural example different from the light-emitting device 100illustrated in FIG. 1 is described below with reference to FIG. 4.

FIG. 4 is a cross-sectional view illustrating an example of alight-emitting device of one embodiment of the present invention. InFIG. 4, a portion having a function similar to that in FIG. 1 isrepresented by the same hatch pattern as in FIG. 1 and not especiallydenoted by a reference numeral in some cases. In addition, commonreference numerals are used for portions having similar functions, and adetailed description of the portions is omitted in some cases.

The light-emitting device 100 illustrated in FIG. 4 includes the firstlight-emitting element 101B, the second light-emitting element 101Y, thethird light-emitting element 101R, and a fourth light-emitting element101G. The first light-emitting element 101B includes the first lowerelectrode 104B, the first transparent conductive layer 106B over thefirst lower electrode 104B, the first light-emitting layer 108 over thefirst transparent conductive layer 106B, the charge-generation layers141 a and 141 b over the first light-emitting layer 108, the secondlight-emitting layer 110 over the charge-generation layers 141 a and 141b, and the upper electrode 112 over the second light-emitting layer 110.The second light-emitting element 101Y includes the second lowerelectrode 104Y, the second transparent conductive layer 106Y over thesecond lower electrode 104Y, the first light-emitting layer 108 over thesecond transparent conductive layer 106Y, the charge-generation layers141 a and 141 b over the first light-emitting layer 108, the secondlight-emitting layer 110 over the charge-generation layers 141 a and 141b, and the upper electrode 112 over the second light-emitting layer 110.The third light-emitting element 101R includes the third lower electrode104R, the third transparent conductive layer 106R over the third lowerelectrode 104R, the first light-emitting layer 108 over the thirdtransparent conductive layer 106R, the charge-generation layers 141 aand 14 lb over the first light-emitting layer 108, the secondlight-emitting layer 110 over the charge-generation layers 141 a and 141b, and the upper electrode 112 over the second light-emitting layer 110.The fourth light-emitting element 101G includes a fourth lower electrode104G, a fourth transparent conductive layer 106G over the fourth lowerelectrode 104G, the first light-emitting layer 108 over the fourthtransparent conductive layer 106G, the charge-generation layers 141 aand 141 b over the first light-emitting layer 108, the secondlight-emitting layer 110 over the charge-generation layers 141 a and 141b, and the upper electrode 112 over the second light-emitting layer 110.

The first light-emitting element 101B further includes the firsttransparent conductive layer 106B, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the first light-emittingelement 101B, the first transparent conductive layer 106B, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the first lower electrode 104B and the first light-emittinglayer 108.

The second light-emitting element 101Y further includes the secondtransparent conductive layer 106Y, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the second light-emittingelement 101Y, the second transparent conductive layer 106Y, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the second lower electrode 104Y and the first light-emittinglayer 108.

The third light-emitting element 101R further includes the thirdtransparent conductive layer 106R, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the third light-emittingelement 101R, the third transparent conductive layer 106R, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the third lower electrode 104R and the first light-emittinglayer 108.

The fourth light-emitting element 101G further includes the fourthtransparent conductive layer 106G, the hole-injection layer 131, thehole-transport layer 132, the electron-transport layer 133, thehole-injection layer 134, the hole-transport layer 135, and theelectron-transport layer 136. Note that in the fourth light-emittingelement 101G, the fourth transparent conductive layer 106G, thehole-injection layer 131, and the hole-transport layer 132 are providedbetween the fourth lower electrode 104G and the first light-emittinglayer 108.

In each of the first light-emitting element 101B, the secondlight-emitting element 101Y, the third light-emitting element 101R, andthe fourth light-emitting element 101G, the electron-transport layer133, the charge-generation layers 141 a and 141 b, the hole-injectionlayer 134, and the hole-transport layer 135 are provided between thefirst light-emitting layer 108 and the second light-emitting layer 110.The electron-transport layer 136 is provided between the secondlight-emitting layer 110 and the upper electrode 112.

Light emitted from the first light-emitting element 101B has at leastone peak in a wavelength range of greater than or equal to 400 nm andless than 480 nm, light emitted from the second light-emitting element101Y has at least one peak in a wavelength range of greater than orequal to 550 nm and less than 600 nm, the light emitted from the thirdlight-emitting element 101R has at least one peak in a wavelength rangeof greater than or equal to 600 nm and less than or equal to 740 nm, andthe light emitted from the fourth light-emitting element 101G has atleast one peak in a wavelength range of greater than or equal to 480 nmand less than 550 nm.

Light emitted from the first light-emitting layer 108 and the secondlight-emitting layer 110 resonates between three pairs of electrodes (apair of the first lower electrode 104B and the upper electrode 112, apair of the second lower electrode 104G and the upper electrode 112, anda pair of the third lower electrode 104R and the upper electrode 112).In the light-emitting device 100 illustrated in FIG. 4, the thickness ofeach of the first transparent conductive layer 106B, the secondtransparent conductive layer 106Y, the third transparent conductivelayer 106R, and the fourth transparent conductive layer 106G in thelight-emitting elements is adjusted so that desired wavelengths of lightemitted from the first light-emitting layer 108 and light emitted fromthe second light-emitting layer 110 can be intensified.

Specifically, the optical path length between the first lower electrode104B and the second light-emitting layer 110 is set to 3λ_(B)/4 (λ_(B)represents a wavelength of blue light) by adjusting the thickness of thefirst transparent conductive layer 106B; the optical path length betweenthe second lower electrode 104Y and the first light-emitting layer 108is set to 3λ_(Y)/4 (λ_(Y) represents a wavelength of yellow light) byadjusting the thickness of the second transparent conductive layer 106Y;the optical path length between the third lower electrode 104R and thefirst light-emitting layer 108 is set to 3λ_(R)/4 (λ_(R) represents awavelength of red light) by adjusting the thickness of the thirdtransparent conductive layer 106R; and the optical path length betweenthe fourth lower electrode 104G and the first light-emitting layer 108is set to 3λ_(G)/4 (λ_(G) represents a wavelength of green light) byadjusting the thickness of the fourth transparent conductive layer 106G.

By adjusting the thickness of the transparent conductive layer of eachlight-emitting element, the optical path length between the first lowerelectrode 104B and the upper electrode 112 is set to λ_(B), the opticalpath length between the second lower electrode 104Y and the upperelectrode 112 is set to 3λ_(Y)/2, the optical path length between thethird lower electrode 104R and the upper electrode 112 is set to3λ_(R)/2, and the optical path length between the fourth lower electrode104G and the upper electrode 112 is set to 3λ_(G)/2.

Note that the optical path length between the third lower electrode 104Rand the upper electrode 112 is not limited to the above-describedoptical path lengths. For example, the optical path length in FIG. 5 canbe obtained by adjusting the thickness of the third transparentconductive layer 106R. FIG. 5 is a cross-sectional view illustrating anexample of a light-emitting device of one embodiment of the presentinvention.

The light-emitting device 100 illustrated in FIG. 5 is the same as thelight-emitting device 100 illustrated in FIG. 4 in the structures of thefirst light-emitting element 101B, the second light-emitting element101Y, and the fourth light-emitting element 101G and is differenttherefrom in the optical path length between the third lower electrode104R and the first light-emitting layer 108 in the third light-emittingelement 101R. Specifically, by adjusting the thickness of the thirdtransparent conductive layer 106R, the optical path length between thethird lower electrode 104R and the first light-emitting layer 108 can beset to approximately λ_(R)/4 (λ_(R) represents a wavelength of redlight). By adjusting the thickness of the third transparent conductivelayer 106R, the optical path length between the third lower electrode104R and the upper electrode 112 can be set to approximately λ_(R).

The other components are similar to those of the light-emitting device100 illustrated in FIG. 1, and the effect similar to that in the case ofthe light-emitting device 100 is obtained.

Structural Example 4 of Light-Emitting Device

Next, a structural example different from the light-emitting device 100illustrated in FIG. 1 is described below with reference to FIGS. 7 to12.

FIGS. 7 to 12 are each a cross-sectional view illustrating an example ofa light-emitting device of one embodiment of the present invention. Ineach of FIGS. 7 to 12, a portion having a function similar to that inFIG. 1 is represented by the same hatch pattern as in FIG. 1 and notespecially denoted by a reference numeral in some cases. In addition,common reference numerals are used for portions having similarfunctions, and a detailed description of the portions is omitted in somecases.

The light-emitting device 100 illustrated in FIG. 7 includes a partitionwall 137 and a substrate 152 in addition to the components of thelight-emitting device 100 illustrated in FIG. 4. The partition walls 137are provided at outer portions of the light-emitting elements and have afunction of covering the end portions of either or both of the lowerelectrodes and the transparent conductive layers of the light-emittingelements. The substrate 152 is provided with a light-blocking layer 154,a first optical element 156R, a second optical element 156Y, a thirdoptical element 156R, and a fourth optical element 156G. Thelight-blocking layer 154 is provided to overlap with the partition wall137. The first optical element 156B, the second optical element 156Y,the third optical element 156R, and the fourth optical element 156G areprovided to overlap with the first light-emitting element 101B, thesecond light-emitting element 101Y, the third light-emitting element101R, and the fourth light-emitting element 101G, respectively.

In the light-emitting device 100 illustrated in FIG. 8, the firstoptical element 156B and the second optical element 156Y of thelight-emitting device 100 illustrated in FIG. 7 are not provided. In thelight-emitting device 100 illustrated in FIG. 9, the second opticalelement 156Y of the light-emitting device 100 illustrated in FIG. 7 isnot provided. In the light-emitting device 100 illustrated in FIG. 10,the first optical element 156B of the light-emitting device 100illustrated in FIG. 7 is not provided.

For example, with the use of a phosphorescent material emitting light ina yellow wavelength range for the first light-emitting layer 108 and afluorescent material emitting light in a blue wavelength range for thesecond light-emitting layer 110, it is possible not to provide anoptical element in at least one of the regions overlapping with thefirst light-emitting element 101B and the second light-emitting element101Y. With a structure in which an optical element is not provided in atleast one of the regions overlapping with the first light-emittingelement 101B and the second light-emitting element 101Y, the powerconsumption of the light-emitting device 100 can be reduced.Particularly when the first light-emitting element 101B is not providedwith the first optical element 156B, power consumption can be reducedmore effectively. Note that to prevent external light reflection, asillustrated in FIG. 7, all of the light-emitting elements are preferredto be provided with the optical elements.

FIG. 11 illustrates the light-emitting device 100 illustrated in FIG. 7,in which transistors are connected to the first light-emitting element101B, the second light-emitting element 101Y, the third light-emittingelement 101R, and the fourth light-emitting element 101G. In thelight-emitting device 100 illustrated in FIG. 11, the lower electrodesof the light-emitting elements are each electrically connected to atransistor 170.

FIG. 12 illustrates the light-emitting device 100 in which the opticalelements (the first optical element 156B, the second optical element156Y, the third optical element 156R, and the fourth optical element156G) are each provided between the transistor 170 and the lowerelectrode. With the structure illustrated in FIG. 12, light extractedfrom the lower electrode is emitted to the substrate 102 side throughthe optical element. Note that with the structure illustrated in FIG.12, in which the optical element or the like is not provided on thesubstrate 152 side, is preferable because manufacturing cost can bereduced.

Note that the transistors 170 included in the light-emitting device 100illustrated in FIGS. 11 and 12 are described in detail with reference toFIG. 13. FIG. 13 is a cross-sectional view of the transistor 170.

The transistor 170 illustrated in FIG. 13 includes a gate electrode 172over the substrate 102, a gate insulating layer 174 over the substrate102 and the gate electrode 172, a semiconductor layer 176 over the gateinsulating layer 174, a source electrode 178 over the gate insulatinglayer 174 and the semiconductor layer 176, and a drain electrode 180over the gate insulating layer 174 and the semiconductor layer 176. Aninsulating layer 182 is provided over the transistor 170, an insulatinglayer 184 is provided over the insulating layer 182, and an insulatinglayer 186 is provided over the insulating layer 184.

The insulating layer 182 is in contact with the semiconductor layer 176.The insulating layer 182 can be formed using an oxide insulatingmaterial, for example. The insulating layer 184 has a function ofsuppressing entry of impurities into the transistor 170. The insulatinglayer 184 can be formed using a nitride insulating material, forexample. The insulating layer 186 has a function of planarizingunevenness and the like due to the transistor 170 and the like. Theinsulating layer 186 can be formed using an organic resin insulatingmaterial, for example.

An opening is formed in the insulating layers 182, 184, and 186. Thedrain electrode 180 of the transistor 170 and the lower electrode (here,the second lower electrode 104Y) are electrically connected to eachother through the opening. Current or voltage flowing through the lowerelectrode can be controlled by driving the transistor 170.

Here, each component of the aforementioned light-emitting device 100 isdescribed below in detail.

The substrate 102 is used as a support of the light-emitting elements.In addition, the substrate 152 is used as a support of the opticalelements. For each of the substrates 102 and 152, glass, quartz,plastic, or the like can be used, for example. Alternatively, a flexiblesubstrate can be used. The flexible substrate is a substrate that can bebent, for example, a plastic substrate made of polycarbonate,polyarylate, or polyethersulfone, and the like. A film (made ofpolypropylene, polyester, poly(vinyl fluoride), poly(vinyl chloride), orthe like), an inorganic film formed by evaporation, or the like can beused. Another material may be used as long as the substrate functions asa support in a manufacturing process of the light-emitting elements oroptical elements.

The light-emitting elements and the optical elements can be formed usinga variety of substrates, for example. The type of substrate is notlimited to a particular type. As the substrate, a semiconductorsubstrate (e.g., a single crystal substrate or a silicon substrate), anSOI substrate, a glass substrate, a quartz substrate, a plasticsubstrate, a metal substrate, a stainless steel substrate, a substrateincluding stainless steel foil, a tungsten substrate, a substrateincluding tungsten foil, a flexible substrate, an attachment film, paperincluding a fibrous material, a base material film, or the like can beused, for example. Examples of the glass substrate include a bariumborosilicate glass substrate, an aluminoborosilicate glass substrate, asoda lime glass substrate, and the like. Examples of the flexiblesubstrate, the attachment film, the base film, and the like aresubstrates of plastics typified by polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyether sulfone (PES), andpolytetrafluoroethylene (PTFE). Another example is a resin such asacrylic. Other examples are polypropylene, polyester, polyvinylfluoride, polyvinyl chloride, and the like. Other examples arepolyamide, polyimide, aramid, epoxy, an inorganic film formed byevaporation, paper, and the like.

Alternatively, a flexible substrate may be used as the substrate, andthe light-emitting elements and the optical elements may be provideddirectly on the flexible substrate. Alternatively, a separation layermay be provided between the substrate and the light-emitting element.Alternatively, a separation layer may be provided between the substrateand the optical element. The separation layer can be used when part orthe whole of the light-emitting elements and the optical elements formedover the separation layer is completed, separated from the substrate,and transferred to another substrate. In such a case, the light-emittingelements and the optical elements can be transferred to a substratehaving low heat resistance or a flexible substrate as well. For theabove-described separation layer, a stack including inorganic films,which are a tungsten film and a silicon oxide film, or an organic resinfilm of polyimide or the like formed over a substrate can be used, forexample.

In other words, after the light-emitting elements and the opticalelements is formed using a substrate, the light-emitting elements andthe optical elements may be transferred to another substrate. Examplesof a substrate to which the light-emitting elements and the opticalelements are transferred include, in addition to the above-describedsubstrates, a paper substrate, a cellophane substrate, an aramid filmsubstrate, a polyimide film substrate, a stone substrate, a woodsubstrate, a cloth substrate (including a natural fiber (e.g., silk,cotton, or hemp), a synthetic fiber (e.g., nylon, polyurethane, orpolyester), a regenerated fiber (e.g., acetate, cupra, rayon, orregenerated polyester), or the like), a leather substrate, a rubbersubstrate, and the like. By using such a substrate, a light-emittingelement and optical element with high durability, a light-emittingelement and optical element with high heat resistance, a lightweightlight-emitting element and optical element, or a thin light-emittingelement and optical element can be obtained.

Lower Electrode

The lower electrodes (the first lower electrode 104B, the second lowerelectrode 104Y, the third lower electrode 104R, and the fourth lowerelectrode 104G) function as anodes of the respective light-emittingelements. The lower electrodes are preferably formed using a reflectiveconductive material. As the conductive material, a conductive materialhaving a visible-light reflectance higher than or equal to 40% and lowerthan or equal to 100%, preferably higher than or equal to 70% and lowerthan or equal to 100%, and a resistivity lower than or equal to 1×10⁻²Ωcm can be used. Specifically, as the lower electrode, silver, aluminum,an alloy containing silver or aluminum, or the like can be used. As thealloy containing aluminum, an alloy containing aluminum, nickel, andlanthanum can be used, for example. Examples of the alloy containingsilver include an alloy containing silver, palladium, and copper, analloy containing silver and copper, an alloy containing silver andmagnesium, an alloy containing silver and nickel, and an alloycontaining silver and gold. The lower electrodes can be formed by asputtering method, an evaporation method, a printing method, a coatingmethod, or the like.

Transparent Conductive Layer

The transparent conductive layers (the first transparent conductivelayer 106B, the second transparent conductive layer 106Y, the thirdtransparent conductive layer 106R, and the fourth transparent conductivelayer 106G) function as part of the lower electrodes of the respectivelight-emitting elements, or the anodes of the respective light-emittingelements. Furthermore, the transparent conductive layer is used toadjust the optical path length between the lower electrode and the upperelectrode in accordance with the desired light wavelength so as toproduce resonance of the desired light emitted from the light-emittinglayer and intensify its wavelength. For example, the thickness of thetransparent conductive layer is adjusted so that the optical path lengthbetween the electrodes can be mλ/2 (m is a natural number), where λ isthe wavelength of a desired light.

As the transparent conductive layer, for example, indium oxide-tin oxide(indium tin oxide (hereinafter referred to as ITO)), indium oxide-tinoxide containing silicon or silicon oxide, indium oxide-zinc oxide(indium zinc oxide), indium oxide containing tungsten oxide and zincoxide, or the like can be used. In particular, a material with a highwork function (4.0 eV or more) is preferably used as the transparentconductive layer. The transparent conductive layer can be formed by asputtering method, an evaporation method, a printing method, a coatingmethod, or the like.

Upper Electrode

The upper electrode 112 functions as a cathode in each of thelight-emitting elements. The upper electrode 112 is preferably formedusing a reflective and light-transmitting conductive material. As theconductive material, a conductive material having a visible-lightreflectance higher than or equal to 20% and lower than or equal to 80%,preferably higher than or equal to 40% and lower than or equal to 70%,and a resistivity lower than or equal to 1×10⁻² Ωcm can be used. Theupper electrode 114 can be formed using one or more kinds of conductivemetals, alloys, conductive compounds, and the like. In particular, it ispreferable to use a material with a low work function (lower than orequal to 3.8 eV). The examples include an element belonging to Group 1or 2 of the periodic table (e.g., an alkali metal such as lithium orcesium, an alkaline earth metal such as calcium or strontium, ormagnesium), an alloy containing any of these elements (e.g., Mg—Ag orAl—Li), a rare earth metal such as europium or ytterbium, an alloycontaining any of these rare earth metals, aluminum, silver, and thelike. The upper electrode 114 can be formed by a sputtering method, anevaporation method, a printing method, a coating method, or the like.

In addition, a bottom-emission light-emitting device can be obtained byinterchanging the materials used for the lower electrode and the upperelectrode with each other as illustrated in FIG. 6 or 12. In the case ofthe bottom-emission light-emitting device, the lower electrode is formedusing a reflective and light-transmitting conductive material, and theupper electrode is formed using a reflective conductive material.

Partition Wall

The partition wall 137 has an insulating property and is formed using aninorganic or organic material. Examples of the inorganic materialinclude a silicon oxide film, a silicon oxynitride film, a siliconnitride oxide film, a silicon nitride film, an aluminum oxide film, analuminum nitride film, and the like. Examples of the organic materialinclude photosensitive resin materials such as an acrylic resin and apolyimide resin.

Light-Emitting Layer

The first light-emitting layer 108 contains a light-emitting materialthat emits light of any one of green, yellow green, yellow, orange, andred, and the second light-emitting layer 110 contains a light-emittingmaterial that emits light of any one of violet, blue, and blue green.The light-emitting material used for the first light-emitting layer 108is preferably a phosphorescent material, and the light-emitting materialused for the second light-emitting layer 110 is preferably a fluorescentmaterial. When a phosphorescent material is used for the firstlight-emitting layer 108 and a fluorescent material is used for thesecond light-emitting layer 110, a light-emitting device with highemission efficiency and high reliability can be obtained. The firstlight-emitting layer 108 and the second light-emitting layer 110 includeeither or both of an electron-transport material and a hole-transportmaterial in addition to the above-described materials.

As the phosphorescent material, a light-emitting substance that convertstriplet excitation energy into light emission can be used. As thefluorescent material, a light-emitting substance that converts singletexcitation energy into light emission can be used. Examples of thelight-emitting substances are described below.

Examples of the light-emitting substance that converts singletexcitation energy into light emission include substances that emitfluorescence. For example, the following substances can be used:substances that emit blue light (emission wavelength: 400 nm to 480 nm)such asN,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N′-bis[4-(9-phenyl-9H-fluoren-9-yephenyl]-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FLPAPm), andN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1.6 mMemFLPAPrn); and substances that emit yellow light(emission wavelength: 540 nm to 580 nm) such as rubrene,5,12-bis(1,1′-biphenyl-4-yl)-6,11-diphenyltetracene (abbreviation: BPT),2-(2-{2-[4-(dimethylamino)phenyl]ethenyl}-6-methyl-4H-pyran-4-ylidene)propanedinitrile (abbreviation: DCM1), and2-{2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene}propanedinitrile (abbreviation: DCM2).

Examples of the light-emitting substance that converts tripletexcitation energy into light emission include substances that emitphosphorescence. For example, a substance having an emission peak at 440nm to 520 nm, a substance having an emission peak at 520 nm to 600 nm,or a substance having an emission peak at 600 nm to 700 nm can be used.

Examples of the substance that has an emission peak at 440 nm to 520 nminclude organometallic iridium complexes having 4H-triazole skeletons,such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN2]phenyl-κC}iridium(III)(abbreviation: Ir(mpptz-dmp)₃),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: Ir(Mptz)₃), andtris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: Ir(iPrptz-3b)₃); organometallic iridium complexes having1H-triazole skeletons, such as tris[3-methyl-1-(2-methylphenyl)-5-phenyl-1H-1,2,4-triazolato]iridium(III)(abbreviation: Ir(Mptz1-mp)₃) andtris(1-methyl-5-phenyl-3-propyl-1H-1,2,4-triazolato)iridium(III)(abbreviation: Ir(Prptz1-Me)₃); organometallic iridium complexes havingimidazole skeletons, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-1H-imidazole] iridium(III)(abbreviation: Ir(iPrpmi)₃) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: Ir(dmpimpt-Me)₃); and organometallic iridium complexes inwhich a phenylpyridine derivative having an electron-withdrawing groupis a ligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III) picolinate (abbreviation: Ir(CF₃ppy)₂(pic)), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(T)]iridium(III)acetylacetonate (abbreviation: FIr(acac)). Among the substances givenabove, the organometallic iridium complex having a 4H-triazole skeletonhas a high reliability and high emission efficiency and is thusespecially preferable.

Examples of the substance that has an emission peak at 520 nm to 600 nminclude organometallic iridium complexes having pyrimidine skeletons,such as tris(4-methyl-6-phenylpyrimidinato)iridium(III) (abbreviation:Ir(mppm)₃), tris(4-t-butyl-6-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)₃),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(mppm)₂(acac)),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(tBuppm)₂(acac)),(acetylacetonato)bis[4-(2-norbornyl)-6-phenylpyrimidinato]iridium(III)(abbreviation: Ir(nbppm)₂(acac)),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: Ir(mpmppm)₂(acac)), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: Ir(dppm)₂(acac)); organometallic iridium complexes havingpyrazine skeletons, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-Me)₂(acac)) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-iPr)₂(acac)); organometallic iridium complexeshaving pyridine skeletons, such astris(2-phenylpyridinato-N,C^(2′))iridium(III) (abbreviation: Ir(ppy)₃),bis(2-phenylpyridinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(ppy)₂(acac)), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: Ir(bzq)₂(acac)),tris(benzo[h]quinolinato)iridium(III) (abbreviation: Ir(bzq)₃),tris(2-phenylquinolinato-N,C^(2′)) iridium(III) (abbreviation: Ir(pq)₃),and bis(2-phenylquinolinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(pq)₂(acac)); and a rare earth metal complex such astris(acetylacetonato) (monophenanthroline)terbium(III) (abbreviation:Tb(acac)₃(Phen)). Among the substances given above, the organometalliciridium complex having a pyrimidine skeleton has distinctively highreliability and emission efficiency and is thus especially preferable.

Among the substances having an emission peak at 520 nm to 600 nm, it isparticularly preferable to use a substance having an emission peak at550 nm to 580 nm for the first light-emitting layer 108. With the use ofthe substance having an emission peak at 550 nm to 580 nm for the firstlight-emitting layer 108, the current efficiency of the light-emittingelement can be increased.

Examples of the substances that has an emission peak at 550 nm to 580 nminclude (acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: Ir(mppm)₂(acac)), (acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium (III)(abbreviation: Ir(tBuppm)₂(acac)),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: Ir(nbppm)₂(acac)),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: Ir(mpmppm)₂(acac)),(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN3]phenyl-κC}iridium(III)(abbreviation: Ir(dmppm-dmp)₂(acac)),(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: Ir(dppm)₂(acac)),(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-Me)₂(acac)),(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: Ir(mppr-iPr)₂(acac)),tris(2-phenylquinolinato-N,C^(2′))iridium(III) (abbreviation: Ir(pq)₃),bis(2-phenylquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(pq)₂(acac)),bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation:Ir(bzq)₂(acac)),bis(2,4-diphenyl-1,3-oxazolato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(dpo)₂(acac)),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: Ir(p-PF-ph)₂(acac)),bis(2-phenylbenzothiazolato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: Ir(bt)₂(acac)), and the like can be used.

Examples of the substance that has an emission peak at 600 nm to 700 nminclude organometallic iridium complexes having pyrimidine skeletons,such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: Ir(5mdppm)₂(dibm)),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: Ir(5mdppm)₂(dpm)), and bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: Ir(d1npm)₂(dpm)); organometallic iridium complexes havingpyrazine skeletons, such as(acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: Ir(tppr)₂(acac)),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: Ir(tppr)₂(dpm)), and(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: Ir(Fdpq)₂(acac)); organometallic iridium complexes havingpyridine skeletons, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:Ir(piq)₃) andbis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate(abbreviation: Ir(piq)₂(acac)); a platinum complex such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: PtOEP); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: Eu(DBM)₃(Phen)) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: Eu(TTA)₃(Phen)). Among the substances given above, theorganometallic iridium complex having a pyrimidine skeleton hasdistinctively high reliability and emission efficiency and is thusespecially preferable. Furthermore, the organometallic iridium complexhaving a pyrazine skeleton can provide red light emission with favorablechromaticity.

As the electron-transport material used for the first light-emittinglayer 108 and the second light-emitting layer 110, a π-electrondeficient heteroaromatic compound such as a nitrogen-containingheteroaromatic compound is preferable. As the electron-transportmaterial, a π-electron deficient heteroaromatic compound, a metalcomplex, or the like can be used. Specific examples include a metalcomplex such as bis(10-hydroxybenzo[h]quinolinato)beryllium(II)(abbreviation: BeBq2),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), bis(8-quinolinolato)zinc(II) (abbreviation: Znq),bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation: ZnPBO), andbis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation: ZnBTZ); aheterocyclic compound having a polyazole skeleton such as2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 2,2′,2″-(1,3,5 -benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI), and2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II); a heterocyclic compound having a diazineskeleton such as 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation: 2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq), 4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine(abbreviation: 4,6mPnP2Pm), and 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine (abbreviation: 4,6mDBTP2Pm-II); aheterocyclic compound having a triazine skeleton such as2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: PCCzPTzn); and a heterocyclic compound having a pyridineskeleton such as 3,5-bis[3-(9H-carbazol-9-yl)phenyl]pyridine(abbreviation: 35DCzPPy) and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene(abbreviation: TmPyPB). Among the above-described materials,heterocyclic compounds having diazine skeletons and triazine skeletonsand heterocyclic compounds having pyridine skeletons have highreliability and are thus preferable. Heterocyclic compounds havingdiazine (pyrimidine or pyrazine) skeletons and triazine skeletons have ahigh electron-transport property and contribute to a decrease in drivevoltage.

As the hole-transport material used for the first light-emitting layer108 and the second light-emitting layer 110, a π-electron deficientheteroaromatic compound or an aromatic amine compound is preferable. Aπ-electron deficient heteroaromatic compound, an aromatic aminecompound, or the like can be preferably used. Specific examples includea compound having an aromatic amine skeleton such as2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF), 4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl(abbreviation: NPB),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD), 4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl (abbreviation:BSPB), 4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:BPAFLP), 4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:mBPAFLP), 4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBA1BP),4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yetriphenylamine (abbreviation:PCBBi1BP), 4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF), N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine (abbreviation: PCBASF), andN-(1,1′-biphenyl-4-yl)-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9,9-dimethyl-9H-fluoren-2-amine(abbreviation: PCBBiF); a compound having a carbazole skeleton such as1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP), and3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP), or9-phenyl-9H-3-(9-phenyl-9H-carbazol-3-yl)carbazole (abbreviation: PCCP);

a compound having a thiophene skeleton such as1,3,5-tri(dibenzothiophen-4-yl)benzene (abbreviation: DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV); and a compound having a furan skeleton suchas 4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzofuran) (abbreviation:DBF3P-II) and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II). Among the above-described materials,compounds having aromatic amine skeletons and compounds having carbazoleskeletons are preferable because these compounds are highly reliable andhave high hole-transport properties to contribute to a reduction indrive voltage.

Furthermore, as the hole-transport material used for the firstlight-emitting layer 108 and the second light-emitting layer 110, a highmolecular compound such as poly(N-vinylcarbazole) (abbreviation: PVK),poly(4-vinyltriphenylamine) (abbreviation: PVTPA), poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N′-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Hole-Injection Layer and Hole-Transport Layer

The hole-injection layer 131 is a layer that injects holes into thefirst light-emitting layer 108 through the hole-transport layer 132 witha high hole-transport property and includes a hole-transport materialand an acceptor substance. When a hole-transport material and anacceptor substance are included, electrons are extracted from thehole-transport material by the acceptor substance to generate holes, andthe holes are injected into the first light-emitting layer 108 throughthe hole-transport layer 132. The hole-injection layer 134 is a layerthat injects holes into the second light-emitting layer 110 through thehole-transport layer 135 with a high hole-transport property andincludes a hole-transport material and an acceptor substance. When ahole-transport material and an acceptor substance are included,electrons are extracted from the hole-transport material by the acceptorsubstance to generate holes, and the holes are injected into the secondlight-emitting layer 110 through the hole-transport layer 135.

Note that the hole-injection layer 131, the hole-transport layer 132,the hole-injection layer 134, and the hole-transport layer 135 areformed using a hole-transport material. As a hole-transport materialused for the hole-injection layer 131, the hole-transport layer 132, thehole-injection layer 134, and the hole-transport layer 135, a materialsimilar to the aforementioned hole-transport material used for the firstlight-emitting layer 108 and the second light-emitting layer 110 can beused.

Examples of the acceptor substance used for the hole-injection layers131 and 134 include an oxide of a metal belonging to any of Group 4 toGroup 8 of the periodic table. Specifically, molybdenum oxide isparticularly preferable.

The hole-injection layer 131 and the hole-transport layer 132 may beformed using a material different between light-emitting layers or witha different thickness in some cases.

Electron-Transport Layer

As an electron-transport material used for the electron-transport layers133 and 136, a material similar to the aforementioned electron-transportmaterial used for the first light-emitting layer 108 and the secondlight-emitting layer 110 can be used.

Electron-Injection Layer

Although not illustrated, a layer with an electron-injection property(an electron-injection layer) may be provided over one or both of theelectron-transport layers 133 and 136. The electron-injection layer is alayer including a substance with a high electron-injection property. Forthe electron-injection layer, an alkali metal, an alkaline earth metal,or a compound thereof, such as lithium fluoride (LiF), cesium fluoride(CsF), calcium fluoride (CaF₂), or lithium oxide (LiO_(x)), can be used.Alternatively, a rare earth metal compound like erbium fluoride (ErF₃)can be used. Electride may also be used for the electron-injectionlayer. Examples of the electride include a substance in which electronsare added at high concentration to calcium oxide-aluminum oxide, and thelike.

Alternatively, the electron-injection layer may be formed using acomposite material in which an organic compound and an electron donor(donor) are mixed. The composite material is superior in anelectron-injection property and an electron-transport property, becauseelectrons are generated in the organic compound by the electron donor.The organic compound here is preferably a material excellent intransporting the generated electrons; specifically, for example, thesubstances for forming the electron-transport layer 133 (e.g., a metalcomplex or a heteroaromatic compound) can be used. As the electrondonor, a substance showing an electron-donating property with respect tothe organic compound is used. Specifically, an alkali metal, an alkalineearth metal, and a rare earth metal are preferable, and lithium, cesium,magnesium, calcium, erbium, ytterbium, and the like are given.

Furthermore, an alkali metal oxide or an alkaline earth metal oxide ispreferable, and for example, lithium oxide, calcium oxide, barium oxide,and the like can be given. Alternatively, Lewis base such as magnesiumoxide can also be used. An organic compound such as tetrathiafulvalene(abbreviation: TTF) can also be used.

The electron-transport layers 133 and 136 and the electron-injectionlayers may be formed using a material different between light-emittinglayers or with a different thickness in some cases.

Charge-Generation Layer

The charge-generation layers 141 a and 141 b has a function of injectingelectrons into one of the light-emitting layers (the firstlight-emitting layer 108 or the second light-emitting layer 110) andinjecting holes into the other light-emitting layer (the firstlight-emitting layer 108 or the second light-emitting layer 110), when avoltage is applied between a pair of electrodes (the lower electrode andthe upper electrode).

For example, in the first light-emitting element 101B illustrated inFIG. 1, when a voltage is applied such that the potential of the firstlower electrode 104B is higher than that of the upper electrode 112, thecharge-generation layer 141 a injects electrons into the firstlight-emitting layer 108 and the charge-generation layer 141 b injectsholes into the second light-emitting layer 110.

Note that in terms of light extraction efficiency, the charge-generationlayers 141 a and 141 b preferably transmit visible light (specifically,the charge-generation layers 141 a and 141 b have a high visible lighttransmittance (e.g., a visible light transmittance higher than or equalto 40%). The charge-generation layers 141 a and 141 b function even ifit has lower conductivity than the pair of electrodes (the lowerelectrode and the upper electrode).

The charge-generation layers 141 a and 141 b can have either a structurein which an acceptor substance is added to a hole-transport material ora structure in which a donor substance is added to an electron-transportmaterial. Alternatively, both of these structures may be stacked.

Note that forming the charge-generation layers 141 a and 141 b by usingany of the above materials can suppress an increase in drive voltagecaused by the stack of the light-emitting layers.

The above-described light-emitting layers, hole-transport layer,hole-injection layer, electron-transport layer, electron-injectionlayer, and charge-generation layers can each be formed by any of thefollowing methods: an evaporation method (including a vacuum evaporationmethod), an ink jet method, a coating method, and the like.

Light-Blocking Layer

The light-blocking layer 154 has a function of reducing the reflectionof external light. The light-blocking layer 154 has a function ofpreventing mixture of light emitted from an adjacent light-emittingelement. As the light-blocking layer 154, a metal, a resin containingblack pigment, carbon black, a metal oxide, a composite oxide containinga solid solution of a plurality of metal oxides, or the like can beused.

Light-Emitting Element

The first optical element 156B, the second optical element 156Y, thethird optical element 156R, and the fourth optical element 156Gselectively transmit light with a particular color out of incidentlight. For example, a color filter, a band pass filter, a multilayerfilter, or the like can be used. Color conversion elements can be usedas the optical elements. A color conversion element is an opticalelement that converts incident light into light having a longerwavelength than the incident light. As the color conversion elements,quantum-dot elements are preferably used. The usage of the quantum-dottype can increase color reproducibility of the light-emitting device.

The first optical element 156B has a function of transmitting light in ablue wavelength range out of light emitted from the first light-emittingelement 101B. The second optical element 156Y has a function oftransmitting light in a yellow wavelength range out of light emittedfrom the second light-emitting element 101Y. The third optical element156R has a function of transmitting light in a red wavelength range outof light emitted from the third light-emitting element 101R. Inaddition, the fourth optical element 156G has a function of transmittinglight in a green wavelength range out of light emitted from the fourthlight-emitting element 101G.

Note that an optical element different from the above-described opticalelements may be provided so as to overlap with each of thelight-emitting elements. As another optical element, for example, acircularly polarizing plate, an anti-reflective film, and the like canbe given. A circularly polarizing plate provided on the side where lightemitted from the light-emitting element of the light-emitting device isextracted can prevent a phenomenon in which light entering from theoutside of the light-emitting device is reflected inside thelight-emitting device and returned to the outside. An anti-reflectivefilm can weaken external light reflected by a surface of thelight-emitting device. Accordingly, light emitted from thelight-emitting device can be observed clearly.

The above-described structures of the light-emitting devices can becombined as appropriate.

Manufacturing Method of Light-Emitting Device

Next, a manufacturing method of a light-emitting device of oneembodiment of the present invention is described below with reference toFIGS. 14A and 14B, FIGS. 15A and 15B, and FIGS. 16A and 16B. Here, amanufacturing method of the light-emitting device 100 illustrated inFIG. 7 is described.

FIGS. 14A and 14B, FIGS. 15A and 15B, and FIGS. 16A and 16B arecross-sectional views for illustrating the manufacturing method of thelight-emitting device of one embodiment of the present invention.

The manufacturing method of the light-emitting device 100 describedbelow includes first to sixth steps.

First Step

The first step is a step for forming the lower electrodes (the firstlower electrode 104B, the second lower electrode 104Y, the third lowerelectrode 104R, and the fourth lower electrode 104G) of thelight-emitting elements, the transparent conductive layers (the firsttransparent conductive layer 106B, the second transparent conductivelayer 106Y, the third transparent conductive layer 106R, and the fourthtransparent conductive layer 106G) of the light-emitting elements, andthe partition wall 137 covering end portions of the lower electrode andthe transparent conductive layer of each light-emitting element (seeFIG. 14A).

In the first step, since there is no possibility of damaging alight-emitting layer containing an organic compound, a variety ofmicromachining technologies can be employed. In this embodiment, areflective conductive film is formed by a sputtering method, subjectedto patterning by a photolithography technique, and then processed intoan island shape by a dry etching method to form the first lowerelectrode 104B, the second lower electrode 104Y, the third lowerelectrode 104R, and the fourth lower electrode 104G.

Next, a light-transmitting conductive film is formed over the firstlower electrode 104B, subjected to patterning by a photolithographytechnique, and then processed into an island shape by a wet etchingmethod to form the first transparent conductive layer 106B. After that,a light-transmitting conductive film is formed over the second lowerelectrode 104Y, subjected to patterning by a photolithography technique,and then processed into island shapes by a wet etching method to formthe second transparent conductive layer 106Y. Next, a light-transmittingconductive film is formed over the third lower electrode 104R, subjectedto patterning by a photolithography technique, and then processed intoisland shapes by a wet etching method to form the third transparentconductive layer 106R. Then, a light-transmitting conductive film isformed over the fourth lower electrode 104G, subjected to patterning bya photolithography technique, and then processed into island shapes by awet etching method to form the fourth transparent conductive layer 106G.

Next, the partition wall 137 is formed to cover end portions of theisland-shaped lower electrode and the island-shaped transparentconductive layer. The partition wall 137 includes an opening overlappingwith the lower electrode. The transparent conductive layer exposed bythe opening functions as part of the lower electrode of thelight-emitting element.

In the first step, an alloy film of silver, palladium, and copper isused as the lower electrode. As the transparent conductive layer, anITSO film is used. As the partition wall 137, a polyimide resin is used.

Note that transistors may be formed over the substrate 102 before thefirst step. The transistors may be electrically connected to the lowerelectrodes (the first lower electrode 104B, the second lower electrode104Y, the third lower electrode 104R, and the fourth lower electrode104G).

Second Step

The second step is a step for forming the hole-injection layer 131, thehole-transport layer 132, the first light-emitting layer 108, and theelectron-transport layer 133 (see FIG. 14B).

The hole-injection layer 131 can be formed by co-evaporating ahole-transport material and a material containing an acceptor substance.Note that co-evaporation is an evaporation method in which a pluralityof different substances are concurrently vaporized from their respectiveevaporation sources. The hole-transport layer 132 can be formed byevaporating a hole-transport material.

The first light-emitting layer 108 can be formed by evaporating alight-emitting substance that emits light of any one of green, yellowgreen, yellow, orange, and red. As the above-described light-emittingsubstance, a phosphorescent organic compound can be used. Thephosphorescent organic compound may be evaporated alone or thephosphorescent organic compound mixed with another material may beevaporated.

For example, the phosphorescent organic compound may be used as a guestmaterial, and the guest material may be dispersed into a host materialhaving a higher excitation energy than the guest material andevaporated.

The electron-transport layer 133 can be formed by evaporating asubstance with a high electron-transport property.

Third Step

The third step is a step for forming the charge-generation layers 141 aand 141 b (see FIG. 15A).

The charge-generation layers 141 a and 141 b can be formed byevaporating a material obtained by adding an electron acceptor(acceptor) to a hole-transport material or a material obtained by addingan electron donor (donor) to an electron-transport material. In thisembodiment, a material obtained by adding an electron donor to anelectron-transport material is used for the charge-generation layer 141a, and a material obtained by adding an electron acceptor to ahole-transport material is used for the charge-generation layer 141 b.

Fourth Step

The fourth step is a step for forming the hole-injection layer 134, thehole-transport layer 135, the second light-emitting layer 110, theelectron-transport layer 136, and the upper electrode 112 (see FIG.15B).

The hole-injection layer 134 can be formed by using a material and amethod which are similar to those of the hole-injection layer 131. Thehole-transport layer 135 can be formed by using a material and a methodwhich are similar to those of the hole-transport layer 132.

The second light-emitting layer 110 can be formed by evaporating alight-emitting substance that emits light of any one of violet, blue,and blue green. As the light-emitting substance, a fluorescent organiccompound can be used. The fluorescent organic compound may be evaporatedalone or the fluorescent organic compound mixed with another materialmay be evaporated. For example, the fluorescent organic compound may beused as a guest material, and the guest material may be dispersed into ahost material having a higher excitation energy than the guest materialand evaporated.

The electron-transport layer 136 can be formed by evaporating asubstance with a high electron-transport property.

The upper electrode 112 can be formed by stacking a reflectiveconductive film and a light-transmitting conductive film.

Through the above-described steps, the first light-emitting element101B, the second light-emitting element 101Y, the third light-emittingelement 101R, and the fourth light-emitting element 101G are formed overthe substrate 102.

Fifth Step

In the fifth step, the light-blocking layer 154, the first opticalelement 156B, the second optical element 156Y, the third optical element156R, and the fourth optical element 156G are formed over the substrate152 (see FIGS. 16A and 16B).

First, the light-blocking layer 154 is formed over the substrate 152(see FIG. 16A).

In this embodiment, as the light-blocking layer 154, an organic resinfilm containing black pigment is formed in a desired region.

Next, the optical elements (the first optical element 156B, the secondoptical element 156Y, the third optical element 156R, and the fourthoptical element 156G) are formed over the substrate 152 and thelight-blocking layer 154 (see FIG. 16B).

In this embodiment, as the first optical element 156B, an organic resinfilm containing blue pigment is formed in a desired region. As thesecond optical element 156Y, an organic resin film containing yellowpigment is formed in a desired region. As the third optical element156R, an organic resin film containing red pigment is formed in adesired region. As the fourth optical element 156G, an organic resinfilm containing green pigment is formed in a desired region.

Through the above steps, the light-blocking layer 154 and the opticalelements (the first optical element 156B, the second optical element156Y, the third optical element 156R, and the fourth optical element156G) are formed over the substrate 152. Note that in this embodiment,the case where the light-blocking layer 154 is formed and then theoptical elements are formed is given as an example; however, withoutlimitation thereto, the light-blocking layer 154 may be formed after theoptical elements are formed, for example.

Sixth Step

In the sixth step, the first light-emitting element 101B, the secondlight-emitting element 101Y, the third light-emitting element 101R, andthe fourth light-emitting element 101G formed over the substrate 102 areattached to the light-blocking layer 154, the first optical element156B, the second optical element 156Y, the third optical element 156R,and the fourth optical element 156G formed over the substrate 152, andsealed with a sealant (not illustrated).

Through the above steps, the light-emitting device 100 illustrated inFIG. 7 can be formed.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 2

In this embodiment, a display device including a light-emitting deviceof one embodiment of the present invention will be described withreference to FIGS. 17A and 17B.

FIG. 17A is a block diagram illustrating the display device of oneembodiment of the present invention, and FIG. 17B is a circuit diagramillustrating a pixel circuit of the display device of one embodiment ofthe present invention.

The display device illustrated in FIG. 17A includes a region includingpixels of display elements (the region is hereinafter referred to as apixel portion 802), a circuit portion provided outside the pixel portion802 and including circuits for driving the pixels (the portion ishereinafter referred to as a driver circuit portion 804), circuitshaving a function of protecting elements (the circuits are hereinafterreferred to as protection circuits 806), and a terminal portion 807.Note that the protection circuits 806 are not necessarily provided.

Part or the whole of the driver circuit portion 804 is preferably formedover a substrate over which the pixel portion 802 is formed, in whichcase the number of components and the number of terminals can bereduced. When part or the whole of the driver circuit portion 804 is notformed over the substrate over which the pixel portion 802 is formed,the part or the whole of the driver circuit portion 804 can be mountedby chip-on-glass (COG) or tape automated bonding (TAB).

The pixel portion 802 includes a plurality of circuits for drivingdisplay elements arranged in X rows (X is a natural number of 2 or more)and Y columns (Y is a natural number of 2 or more) (such circuits arehereinafter referred to as pixel circuits 801). The driver circuitportion 804 includes driver circuits such as a circuit for supplying asignal (scan signal) to select a pixel (the circuit is hereinafterreferred to as a gate driver 804 a) and a circuit for supplying a signal(data signal) to drive a display element in a pixel (the circuit ishereinafter referred to as a source driver 804 b).

The gate driver 804 a includes a shift register or the like. Through theterminal portion 807, the gate driver 804 a receives a signal fordriving the shift register and outputs a signal. For example, the gatedriver 804 a receives a start pulse signal, a clock signal, or the likeand outputs a pulse signal. The gate driver 804 a has a function ofcontrolling the potentials of wirings supplied with scan signals (suchwirings are hereinafter referred to as scan lines GL_1 to GL_(')X). Notethat a plurality of gate drivers 804 a may be provided to control thescan lines GL_1 to GL_X separately. Alternatively, the gate driver 804 ahas a function of supplying an initialization signal. Without beinglimited thereto, the gate driver 804 a can supply another signal.

The source driver 804 b includes a shift register or the like. Thesource driver 804 b receives a signal (video signal) from which a datasignal is derived, as well as a signal for driving the shift register,through the terminal portion 807. The source driver 804 b has a functionof generating a data signal to be written to the pixel circuit 801 whichis based on the video signal. In addition, the source driver 804 b has afunction of controlling output of a data signal in response to a pulsesignal produced by input of a start pulse signal, a clock signal, or thelike. Furthermore, the source driver 804 b has a function of controllingthe potentials of wirings supplied with data signals (such wirings arehereinafter referred to as data lines DL_1 to DL_Y). Alternatively, thesource driver 804 b has a function of supplying an initializationsignal. Without being limited thereto, the source driver 804 b cansupply another signal.

The source driver 804 b includes a plurality of analog switches or thelike, for example. The source driver 804 b can output, as the datasignals, signals obtained by time-dividing the video signal bysequentially turning on the plurality of analog switches.

A pulse signal and a data signal are input to each of the plurality ofpixel circuits 801 through one of the plurality of scan lines GLsupplied with scan signals and one of the plurality of data lines DLsupplied with data signals, respectively. Writing and holding of thedata signal to and in each of the plurality of pixel circuits 801 arecontrolled by the gate driver 804 a. For example, to the pixel circuit801 in the m-th row and the n-th column (m is a natural number of lessthan or equal to X, and n is a natural number of less than or equal toY), a pulse signal is input from the gate driver 804 a through the scanline GL_m, and a data signal is input from the source driver 804 bthrough the data line DL_n in accordance with the potential of the scanline GL_m.

The protection circuit 806 illustrated in FIG. 17A is connected to, forexample, the scan line GL between the gate driver 804 a and the pixelcircuit 801. Alternatively, the protection circuit 806 is connected tothe data line DL between the source driver 804 b and the pixel circuit801. Alternatively, the protection circuit 806 can be connected to awiring between the gate driver 804 a and the terminal portion 807.Alternatively, the protection circuit 806 can be connected to a wiringbetween the source driver 804 b and the terminal portion 807. Note thatthe terminal portion 807 means a portion having terminals for inputtingpower, control signals, and video signals to the display device fromexternal circuits.

The protection circuit 806 is a circuit that electrically connects awiring connected to the protection circuit to another wiring when apotential out of a certain range is applied to the wiring connected tothe protection circuit.

As illustrated in FIG. 17A, the protection circuits 806 are provided forthe pixel portion 802 and the driver circuit portion 804, so that theresistance of the display device to overcurrent generated byelectrostatic discharge (ESD) or the like can be improved. Note that theconfiguration of the protection circuits 806 is not limited to that, andfor example, a configuration in which the protection circuits 806 areconnected to the gate driver 804 a or a configuration in which theprotection circuits 806 are connected to the source driver 804 b may beemployed. Alternatively, the protection circuits 806 may be configuredto be connected to the terminal portion 807.

In FIG. 17A, an example in which the driver circuit portion 804 includesthe gate driver 804 a and the source driver 804 b is shown; however, thestructure is not limited thereto. For example, only the gate driver 804a may be formed and a separately prepared substrate where a sourcedriver circuit is formed (e.g., a driver circuit substrate formed with asingle crystal semiconductor film or a polycrystalline semiconductorfilm) may be mounted.

Each of the plurality of pixel circuits 801 in FIG. 17A can have astructure illustrated in FIG. 17B, for example.

The pixel circuit 801 illustrated in FIG. 17B includes transistors 852and 854, a capacitor 862, and a light-emitting element 872.

One of a source electrode and a drain electrode of the transistor 852 iselectrically connected to a wiring to which a data signal is supplied(hereinafter referred to as a data line DL_n). A gate electrode of thetransistor 852 is electrically connected to a wiring to which a gatesignal is supplied (hereinafter referred to as a scan line GL_m).

The transistor 852 has a function of controlling whether to write a datasignal by being turned on or off.

One of a pair of electrodes of the capacitor 862 is electricallyconnected to a wiring to which a potential is supplied (hereinafterreferred to as a potential supply line VL_a), and the other iselectrically connected to the other of the source electrode and thedrain electrode of the transistor 852.

The capacitor 862 functions as a storage capacitor for storing writtendata.

One of a source electrode and a drain electrode of the transistor 854 iselectrically connected to the potential supply line VL_a. Furthermore, agate electrode of the transistor 854 is electrically connected to theother of the source electrode and the drain electrode of the transistor852.

One of an anode and a cathode of the light-emitting element 872 iselectrically connected to a potential supply line VL_b, and the other iselectrically connected to the other of the source electrode and thedrain electrode of the transistor 854.

As the light-emitting element 872, any of the light-emitting elementsdescribed in Embodiment 1 can be used.

Note that a high power supply potential VDD is supplied to one of thepotential supply line VL_a and the potential supply line VL_b, and a lowpower supply potential VSS is supplied to the other.

In the display device including the pixel circuits 801 in FIG. 17B, thepixel circuits 801 are sequentially selected row by row by the gatedriver 804 a in FIG. 17A, for example, whereby the transistors 852 areturned on and a data signal is written.

When the transistors 852 are turned off, the pixel circuits 801 in whichthe data has been written are brought into a holding state. Furthermore,the amount of current flowing between the source electrode and the drainelectrode of the transistor 854 is controlled in accordance with thepotential of the written data signal. The light-emitting element 872emits light with a luminance corresponding to the amount of flowingcurrent. This operation is sequentially performed row by row; thus, animage is displayed.

Alternatively, the pixel circuit can have a function of compensatingvariation in threshold voltages or the like of a transistor. FIGS. 18Aand 18B and FIGS. 19A and 19B illustrate examples of the pixel circuit.

The pixel circuit illustrated in FIG. 18A includes six transistors(transistors 303_1 to 303_6), a capacitor 304, and a light-emittingelement 305. The pixel circuit illustrated in FIG. 18A is electricallyconnected to wirings 301_1 to 301_5 and wirings 302_1 and 302_2. Notethat as the transistors 303_1 to 303_6, for example, p-channeltransistors can be used.

The pixel circuit illustrated in FIG. 18B has a configuration in which atransistor 303_7 is added to the pixel circuit illustrated in FIG. 18A.The pixel circuit illustrated in FIG. 18B is electrically connected towirings 301_6 and 301_7. The wirings 301_5 and 301_6 may be electricallyconnected to each other. Note that as the transistor 303_7, for example,a p-channel transistor can be used.

The pixel circuit illustrated in FIG. 19A includes six transistors(transistors 308_1 to 308_6), the capacitor 304, and the light-emittingelement 305. The pixel circuit illustrated in FIG. 19A is electricallyconnected to wirings 306_1 to 306_3 and wirings 307_1 to 307_3. Thewirings 306_1 and 306_3 may be electrically connected to each other.Note that as the transistors 308_1 to 308_6, for example, p-channeltransistors can be used.

The pixel circuit illustrated in FIG. 19B includes two transistors(transistors 309_1 and 309_2), two capacitors (capacitors 304_1 and304_2), and the light-emitting element 305. The pixel circuitillustrated in FIG. 19B is electrically connected to wirings 311_1 to311_3 and wirings 312_1 and 312_2. With the configuration of the pixelcircuit illustrated in FIG. 19B, the light-emitting element 305 can bedriven by constant voltage constant current (CVCC). Note that as thetransistors 309_1 and 309_2, for example, p-channel transistors can beused.

A light-emitting element of one embodiment of the present invention canbe used for an active matrix method in which an active element isincluded in a pixel of a display device or a passive matrix method inwhich an active element is not included in a pixel of a display device.

In the active matrix method, as an active element (a non-linearelement), not only a transistor but also a variety of active elements(non-linear elements) can be used. For example, a metal insulator metal(MIM), a thin film diode (TFD), or the like can also be used. Sincethese elements can be formed with a smaller number of manufacturingsteps, manufacturing cost can be reduced or yield can be improved.Alternatively, since the size of these elements is small, the apertureratio can be improved, so that power consumption can be reduced orhigher luminance can be achieved.

As a method other than the active matrix method, the passive matrixmethod in which an active element (a non-linear element) is not used canalso be used. Since an active element (a non-linear element) is notused, the number of manufacturing steps is small, so that manufacturingcost can be reduced or yield can be improved. Alternatively, since anactive element (a non-linear element) is not used, the aperture ratiocan be improved, so that power consumption can be reduced or higherluminance can be achieved, for example.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 3

In this embodiment, a display panel including a light-emitting device ofone embodiment of the present invention and an electronic device inwhich the display panel is provided with an input device will bedescribed with reference to FIGS. 20A and 20B, FIGS. 21A to 21C, FIGS.22A and 22B, FIGS. 23A and 23B, and FIG. 24.

Description 1 of Touch Panel

In this embodiment, a touch panel 2000 including a display panel and aninput device will be described as an example of an electronic device. Inaddition, an example in which a touch sensor is used as an input devicewill be described. Note that a light-emitting device of one embodimentof the present invention can be used for a pixel of the display panel.

FIGS. 20A and 20B are perspective views of the touch panel 2000. Notethat FIGS. 20A and 20B illustrate only main components of the touchpanel 2000 for simplicity.

The touch panel 2000 includes a display panel 2501 and a touch sensor2595 (see FIG. 20B). The touch panel 2000 also includes a substrate2510, a substrate 2570, and a substrate 2590. The substrate 2510, thesubstrate 2570, and the substrate 2590 each have flexibility. Note thatone or all of the substrates 2510, 2570, and 2590 may be inflexible.

The display panel 2501 includes a plurality of pixels over the substrate2510 and a plurality of wirings 2511 through which signals are suppliedto the pixels. The plurality of wirings 2511 are led to an outer portionof the substrate 2510, and part of the plurality of wirings 2511 form aterminal 2519. The terminal 2519 is electrically connected to an FPC2509(1).

The substrate 2590 includes the touch sensor 2595 and a plurality ofwirings 2598 electrically connected to the touch sensor 2595. Theplurality of wirings 2598 are led to an outer portion of the substrate2590, and part of the plurality of wirings 2598 form a terminal. Theterminal is electrically connected to an FPC 2509(2). Note that in FIG.20B, electrodes, wirings, and the like of the touch sensor 2595 providedon the back side of the substrate 2590 (the side facing the substrate2510) are indicated by solid lines for clarity.

As the touch sensor 2595, a capacitive touch sensor can be used.Examples of the capacitive touch sensor include a surface capacitivetouch sensor and a projected capacitive touch sensor.

Examples of the projected capacitive touch sensor are a self capacitivetouch sensor and a mutual capacitive touch sensor, which differ mainlyin the driving method. The use of a mutual capacitive type is preferablebecause multiple points can be sensed simultaneously.

Note that the touch sensor 2595 illustrated in FIG. 20B is an example ofusing a projected capacitive touch sensor.

Note that a variety of sensors that can sense proximity or touch of asensing target such as a finger can be used as the touch sensor 2595.

The projected capacitive touch sensor 2595 includes electrodes 2591 andelectrodes 2592. The electrodes 2591 are electrically connected to anyof the plurality of wirings 2598, and the electrodes 2592 areelectrically connected to any of the other wirings 2598.

The electrodes 2592 each have a shape of a plurality of quadranglesarranged in one direction with one corner of a quadrangle connected toone corner of another quadrangle as illustrated in FIGS. 20A and 20B.

The electrodes 2591 each have a quadrangular shape and are arranged in adirection intersecting with the direction in which the electrodes 2592extend.

A wiring 2594 electrically connects two electrodes 2591 between whichthe electrode 2592 is positioned. The intersecting area of the electrode2592 and the wiring 2594 is preferably as small as possible. Such astructure allows a reduction in the area of a region where theelectrodes are not provided, reducing variation in transmittance. As aresult, variation in luminance of light passing through the touch sensor2595 can be reduced.

Note that the shapes of the electrodes 2591 and the electrodes 2592 arenot limited thereto and can be any of a variety of shapes. For example,a structure may be employed in which the plurality of electrodes 2591are arranged so that gaps between the electrodes 2591 are reduced asmuch as possible, and the electrodes 2592 are spaced apart from theelectrodes 2591 with an insulating layer interposed therebetween to haveregions not overlapping with the electrodes 2591. In this case, it ispreferable to provide, between two adjacent electrodes 2592, a dummyelectrode electrically insulated from these electrodes because the areaof regions having different transmittances can be reduced.

Note that for example, a transparent conductive film including indiumoxide, tin oxide, zinc oxide, or the like (e.g., a film of ITO) can begiven as a material of conductive films used for the electrode 2591, theelectrode 2592, and the wiring 2598, i.e., wirings and electrodes in thetouch panel. Moreover, for example, a low-resistance material ispreferably used as the material of the wiring and the electrode in thetouch panel. For example, silver, copper, aluminum, a carbon nanotube,graphene, a metal halide (such as a silver halide), or the like may beused. Alternatively, a metal nanowire including a plurality ofconductors with an extremely small width (e.g., a diameter of severalnanometers) may be used. Further alternatively, a net-like metal meshwith a conductor may be used. Examples of such materials include an Agnanowire, a Cu nanowire, an Al nanowire, an Ag mesh, a Cu mesh, and anAl mesh. For example, in the case of using an Ag nanowire for the wiringand the electrode in the touch panel, a visible light transmittance of89% or more and a sheet resistance of 40 Ω/sq. or more and 100 Ω/sq. orless can be achieved. A metal nanowire, a metal mesh, a carbon nanotube,graphene, and the like, which are examples of a material that can beused for the above-described wiring and electrode in the touch panel,have a high visible light transmittance; therefore, they may be used foran electrode of a display element (e.g., a pixel electrode or a commonelectrode).

Display Panel

Next, the display panel 2501 is described in detail with reference toFIG. 21A. FIG. 21A is a cross-sectional view along dashed-dotted lineX1-X2 in FIG. 20B.

The display panel 2501 includes a plurality of pixels arranged in amatrix. Each of the pixels includes a display element and a pixelcircuit for driving the display element.

For the substrate 2510 and the substrate 2570, for example, a flexiblematerial with a vapor permeability lower than or equal to 10⁻⁵g/(m²·day), preferably lower than or equal to 1×10⁻⁶ g/(m²·day) can bepreferably used. Alternatively, materials whose thermal expansioncoefficients are substantially equal to each other are preferably usedfor the substrate 2510 and the substrate 2570. For example, thecoefficients of linear expansion of the materials are preferably lowerthan or equal to 1×10⁻³/K, further preferably lower than or equal to5×10⁻⁵/K and still further preferably lower than or equal to 1×10⁻⁵/K.

Note that the substrate 2510 is a stacked body including an insulatinglayer 2510 a for preventing impurity diffusion into the light-emittingelement, a flexible substrate 2510 b, and an adhesive layer 2510 c forattaching the insulating layer 2510 a and the flexible substrate 2510 bto each other. The substrate 2570 is a stacked body including aninsulating layer 2570 a for preventing impurity diffusion into thelight-emitting element, a flexible substrate 2570 b, and an adhesivelayer 2570 c for attaching the insulating layer 2570 a and the flexiblesubstrate 2570 b to each other.

For the adhesive layer 2510 c and the adhesive layer 2570 c, forexample, materials that include polyester, polyolefin, polyamide (e.g.,nylon or aramid), polyimide, polycarbonate, polyurethane, an acrylicresin, an epoxy resin, or a resin having a siloxane bond can be used.

A sealing layer 2560 is provided between the substrate 2510 and thesubstrate 2570. The sealing layer 2560 preferably has a refractive indexhigher than that of air. In the case where light is extracted to thesealing layer 2560 side as illustrated in FIG. 21A, the sealing layer2560 can also serve as an optical element.

A sealant may be formed in the outer portion of the sealing layer 2560.With the use of the sealant, a light-emitting element 2550 can beprovided in a region surrounded by the substrate 2510, the substrate2570, the sealing layer 2560, and the sealant. Note that an inert gas(such as nitrogen or argon) may be used instead of the sealing layer2560. A drying agent may be provided in the inert gas so as to adsorbmoisture or the like. For example, an epoxy-based resin or a glass fritis preferably used as the sealant. As a material used for the sealant, amaterial which is impermeable to moisture or oxygen is preferably used.

The display panel 2501 includes a pixel 2502. The pixel 2502 includes alight-emitting module 2580.

The pixel 2502 includes the light-emitting element 2550 and a transistor2502 t that can supply electric power to the light-emitting element2550. Note that the transistor 2502 t functions as part of the pixelcircuit. The light-emitting module 2580 includes the light-emittingelement 2550 and a coloring layer 2567R.

The light-emitting element 2550 includes a lower electrode, an upperelectrode, and an EL layer between the lower electrode and the upperelectrode. As the light-emitting element 2550, any of the light-emittingelements described in Embodiment 1 can be used, for example. Note thatalthough only one light-emitting element 2550 is illustrated in FIG.21A, it is possible to employ the structure with two or more kinds oflight-emitting elements as described in Embodiment 1.

In the case where the sealing layer 2560 is provided on the lightextraction side, the sealing layer 2560 is in contact with thelight-emitting element 2550 and the coloring layer 2567R.

The coloring layer 2567R is provided to overlap with the light-emittingelement 2550. Accordingly, part of light emitted from the light-emittingelement 2550 passes through the coloring layer 2567R and is emitted tothe outside of the light-emitting module 2580 as indicated by an arrowin FIG. 21A.

The display panel 2501 includes a light-blocking layer 2567BM on thelight extraction side. The light-blocking layer 2567BM is provided so asto surround the coloring layer 2567R.

The coloring layer 2567R is a coloring layer having a function oftransmitting light in a particular wavelength range. For example, acolor filter for transmitting light in a red wavelength range, a colorfilter for transmitting light in a green wavelength range, a colorfilter for transmitting light in a blue wavelength range, a color filterfor transmitting light in a yellow wavelength range, or the like can beused. Each color filter can be formed with any of various materials by aprinting method, an ink-jet method, an etching method using aphotolithography technique, or the like.

An insulating layer 2521 is provided in the display panel 2501. Theinsulating layer 2521 covers the transistor 2502 t. Note that theinsulating layer 2521 has a function of planarizing unevenness caused bythe pixel circuit. The insulating layer 2521 may have a function ofsuppressing impurity diffusion. This can prevent the reliability of thetransistor 2502 t or the like from being lowered by impurity diffusion.

The light-emitting element 2550 is formed over the insulating layer2521. A partition wall 2528 is provided so as to overlap with an endportion of the lower electrode of the light-emitting element 2550. Notethat a spacer for controlling the distance between the substrate 2510and the substrate 2570 may be formed over the partition wall 2528.

A scan line driver circuit 2503 g includes a transistor 2503 t and acapacitor 2503 c. Note that the driver circuit can be formed in the sameprocess and over the same substrate as those of the pixel circuits.

The wirings 2511 through which signals can be supplied are provided overthe substrate 2510. The terminal 2519 is provided over the wiring 2511.The FPC 2509(1) is electrically connected to the terminal 2519. The FPC2509(1) has a function of supplying a video signal, a clock signal, astart signal, a reset signal, or the like. Note that the FPC 2509(1) maybe provided with a printed wiring board (PWB).

In the display panel 2501, transistors with any of a variety ofstructures can be used. FIG. 21A illustrates an example of usingbottom-gate transistors; however, the present invention is not limitedto this example, and top-gate transistors may be used in the displaypanel 2501 as illustrated in FIG. 21B.

In addition, there is no particular limitation on the polarity of thetransistor 2502 t and the transistor 2503 t. For these transistors,n-channel and p-channel transistors may be used, or either n-channeltransistors or p-channel transistors may be used, for example.Furthermore, there is no particular limitation on the crystallinity of asemiconductor film used for the transistors 2502 t and 2503 t. Forexample, an amorphous semiconductor film or a crystalline semiconductorfilm may be used. Examples of semiconductor materials include Group 13semiconductors (e.g., a semiconductor including gallium), Group 14semiconductors (e.g., a semiconductor including silicon), compoundsemiconductors (including oxide semiconductors), organic semiconductors,and the like. It is preferable to use an oxide semiconductor that has anenergy gap of 2 eV or more, preferably 2.5 eV or more and furtherpreferably 3 eV or more, for one of the transistors 2502 t and 2503 t orboth, in which case the off-state current of the transistors can bereduced. Examples of the oxide semiconductors include an In—Ga oxide, anIn—M—Zn oxide (M represents Al, Ga, Y, Zr, La, Ce, Sn, or Nd), and thelike.

Touch Sensor

Next, the touch sensor 2595 is described in detail with reference toFIG. 21C. FIG. 21C is a cross-sectional view along dashed-dotted lineX3-X4 in FIG. 20B.

The touch sensor 2595 includes the electrodes 2591 and the electrodes2592 provided in a staggered arrangement on the substrate 2590, aninsulating layer 2593 covering the electrodes 2591 and the electrodes2592, and the wiring 2594 that electrically connects the adjacentelectrodes 2591 to each other.

The electrodes 2591 and the electrodes 2592 are formed usinglight-transmitting conductive material. As a light-transmittingconductive material, a conductive oxide such as indium oxide, indium tinoxide, indium zinc oxide, zinc oxide, or zinc oxide to which gallium isadded can be used. Note that a film including graphene may be used aswell. The film including graphene can be formed, for example, byreducing a film containing graphene oxide. As a reducing method, amethod with application of heat or the like can be employed.

The electrodes 2591 and the electrodes 2592 may be formed by, forexample, depositing a light-transmitting conductive material on thesubstrate 2590 by a sputtering method and then removing an unnecessaryportion by any of various pattern forming techniques such asphotolithography.

Examples of a material for the insulating layer 2593 are a resin such asan acrylic resin or an epoxy resin, a resin having a siloxane bond, andan inorganic insulating material such as silicon oxide, siliconoxynitride, or aluminum oxide.

Openings reaching the electrodes 2591 are formed in the insulating layer2593, and the wiring 2594 electrically connects the adjacent electrodes2591. A light-transmitting conductive material can be preferably used asthe wiring 2594 because the aperture ratio of the touch panel can beincreased. Moreover, a material with higher conductivity than theconductivities of the electrodes 2591 and 2592 can be preferably usedfor the wiring 2594 because electric resistance can be reduced.

One electrode 2592 extends in one direction, and a plurality ofelectrodes 2592 are provided in the form of stripes. The wiring 2594intersects with the electrode 2592.

Adjacent electrodes 2591 are provided with one electrode 2592 providedtherebetween. The wiring 2594 electrically connects the adjacentelectrodes 2591.

Note that the plurality of electrodes 2591 are not necessarily arrangedin the direction orthogonal to one electrode 2592 and may be arranged tointersect with one electrode 2592 at an angle of more than 0 degrees andless than 90 degrees.

The wiring 2598 is electrically connected to any of the electrodes 2591and 2592. Part of the wiring 2598 functions as a terminal. For thewiring 2598, a metal material such as aluminum, gold, platinum, silver,nickel, titanium, tungsten, chromium, molybdenum, iron, cobalt, copper,or palladium or an alloy material containing any of these metalmaterials can be used.

Note that an insulating layer that covers the insulating layer 2593 andthe wiring 2594 may be provided to protect the touch sensor 2595.

A connection layer 2599 electrically connects the wiring 2598 to the FPC2509(2).

As the connection layer 2599, any of various anisotropic conductivefilms (ACF), anisotropic conductive pastes (ACP), or the like can beused.

Description 2 of Touch Panel

Next, the touch panel 2000 is described in detail with reference to FIG.22A. FIG. 22A is a cross-sectional view along dashed-dotted line X5-X6in FIG. 20A.

In the touch panel 2000 illustrated in FIG. 22A, the display panel 2501described with reference to FIG. 21A and the touch sensor 2595 describedwith reference to FIG. 21C are attached to each other.

The touch panel 2000 illustrated in FIG. 22A includes an adhesive layer2597 and an anti-reflective layer 2567 p in addition to the componentsdescribed with reference to FIGS. 21A and 21C.

The adhesive layer 2597 is provided in contact with the wiring 2594.Note that the adhesive layer 2597 attaches the substrate 2590 to thesubstrate 2570 so that the touch sensor 2595 overlaps with the displaypanel 2501. The adhesive layer 2597 preferably has a light-transmittingproperty. A heat curable resin or an ultraviolet curable resin can beused for the adhesive layer 2597. For example, an acrylic resin, anurethane-based resin, an epoxy-based resin, or a siloxane-based resincan be used.

The anti-reflective layer 2567 p is provided to overlap with pixels. Asthe anti-reflective layer 2567 p, a circularly polarizing plate can beused, for example.

Next, a touch panel having a structure different from that illustratedin FIG. 22A is described with reference to FIG. 22B.

FIG. 22B is a cross-sectional view of a touch panel 2001. The touchpanel 2001 illustrated in FIG. 22B differs from the touch panel 2000illustrated in FIG. 22A in the position of the touch sensor 2595relative to the display panel 2501. Different parts are described indetail below, and the above description of the touch panel 2000 isreferred to for the other similar parts.

The coloring layer 2567R is provided to overlap with the light-emittingelement 2550. The light-emitting element 2550 illustrated in FIG. 22Bemits light to the side where the transistor 2502 t is provided.Accordingly, part of light emitted from the light-emitting element 2550passes through the coloring layer 2567R and is emitted to the outside ofthe light-emitting module 2580 as indicated by an arrow in FIG. 22B.

The touch sensor 2595 is provided on the substrate 2510 side of thedisplay panel 2501.

The adhesive layer 2597 is provided between the substrate 2510 and thesubstrate 2590 and attaches the touch sensor 2595 to the display panel2501.

As illustrated in FIG. 22A or 22B, light may be emitted from thelight-emitting element to one of upper and lower sides, or both, of thesubstrate.

Method for Driving Touch Panel

Next, an example of a method for driving a touch panel is described withreference to FIGS. 23A and 23B.

FIG. 23A is a block diagram illustrating the structure of a mutualcapacitive touch sensor. FIG. 23A illustrates a pulse voltage outputcircuit 2601 and a current sensing circuit 2602. Note that in FIG. 23A,six wirings X1 to X6 represent the electrodes 2621 to which a pulsevoltage is applied, and six wirings Y1 to Y6 represent the electrodes2622 that detect changes in current. FIG. 23A also illustratescapacitors 2603 that are each formed in a region where the electrodes2621 and 2622 overlap with each other. Note that functional replacementbetween the electrodes 2621 and 2622 is possible.

The pulse voltage output circuit 2601 is a circuit for sequentiallyapplying a pulse voltage to the wirings X1 to X6. By application of apulse voltage to the wirings X1 to X6, an electric field is generatedbetween the electrodes 2621 and 2622 of the capacitor 2603. When theelectric field between the electrodes is shielded, for example, a changeoccurs in the capacitor 2603 (mutual capacitance). The approach orcontact of a sensing target can be sensed by utilizing this change.

The current sensing circuit 2602 is a circuit for detecting changes incurrent flowing through the wirings Y1 to Y6 that are caused by thechange in mutual capacitance in the capacitor 2603. No change in currentvalue is detected in the wirings Y1 to Y6 when there is no approach orcontact of a sensing target, whereas a decrease in current value isdetected when mutual capacitance is decreased owing to the approach orcontact of a sensing target. Note that an integrator circuit or the likeis used for detection of current values.

FIG. 23B is a timing chart showing input and output waveforms in themutual capacitive touch sensor illustrated in FIG. 23A. In FIG. 23B,sensing of a sensing target is performed in all the rows and columns inone frame period. FIG. 23B shows a period when a sensing target is notsensed (not touched) and a period when a sensing target is sensed(touched). Sensed current values of the wirings Y1 to Y6 are shown asthe waveforms of voltage values.

A pulse voltage is sequentially applied to the wirings X1 to X6, and thewaveforms of the wirings Y1 to Y6 change in accordance with the pulsevoltage. When there is no approach or contact of a sensing target, thewaveforms of the wirings Y1 to Y6 change in accordance with changes inthe voltages of the wirings X1 to X6. The current value is decreased atthe point of approach or contact of a sensing target and accordingly thewaveform of the voltage level changes.

By detecting a change in mutual capacitance in this manner, proximity orcontact of a sensing target can be sensed.

Sensor Circuit

Although FIG. 23A illustrates a passive type touch sensor in which onlythe capacitor 2603 is provided at the intersection of wirings as a touchsensor, an active type touch sensor including a transistor and acapacitor may be used. FIG. 24 illustrates an example of a sensorcircuit included in an active type touch sensor.

The sensor circuit in FIG. 24 includes the capacitor 2603 andtransistors 2611, 2612, and 2613.

A signal G2 is input to a gate of the transistor 2613. A voltage VRES isapplied to one of a source and a drain of the transistor 2613, and oneelectrode of the capacitor 2603 and a gate of the transistor 2611 areelectrically connected to the other of the source and the drain of thetransistor 2613. One of a source and a drain of the transistor 2611 iselectrically connected to one of a source and a drain of the transistor2612, and a voltage VSS is applied to the other of the source and thedrain of the transistor 2611. A signal G1 is input to a gate of thetransistor 2612, and a wiring ML is electrically connected to the otherof the source and the drain of the transistor 2612. The voltage VSS isapplied to the other electrode of the capacitor 2603.

Next, the operation of the sensor circuit in FIG. 24 is described.First, a potential for turning on the transistor 2613 is supplied as thesignal G2, and a potential with respect to the voltage VRES is thusapplied to the node n connected to the gate of the transistor 2611.Then, a potential for turning off the transistor 2613 is applied as thesignal G2, whereby the potential of the node n is maintained.

Then, mutual capacitance of the capacitor 2603 changes owing to theapproach or contact of a sensing target such as a finger, andaccordingly the potential of the node n is changed from VRES.

In reading operation, a potential for turning on the transistor 2612 issupplied as the signal G1. A current flowing through the transistor2611, that is, a current flowing through the wiring ML is changed inaccordance with the potential of the node n. By sensing this current,the approach or contact of a sensing target can be sensed.

In each of the transistors 2611, 2612, and 2613, an oxide semiconductorlayer is preferably used as a semiconductor layer in which a channelregion is formed. In particular, such a transistor is preferably used asthe transistor 2613 so that the potential of the node n can be held fora long time and the frequency of operation of resupplying VRES to thenode n (refresh operation) can be reduced.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 4

In this embodiment, a display module and electronic devices including alight-emitting device of one embodiment of the present invention will bedescribed with reference to FIG. 25 and FIGS. 26A to 26G.

In a display module 8000 illustrated in FIG. 25, a touch sensor 8004connected to an FPC 8003, a display panel 8006 connected to an FPC 8005,a frame 8009, a printed board 8010, and a battery 8011 are providedbetween an upper cover 8001 and a lower cover 8002.

The light-emitting device of one embodiment of the present invention canbe used for the display panel 8006, for example.

The shapes and sizes of the upper cover 8001 and the lower cover 8002can be changed as appropriate in accordance with the sizes of the touchsensor 8004 and the display panel 8006.

The touch sensor 8004 can be a resistive touch sensor or a capacitivetouch sensor and may be formed to overlap with the display panel 8006. Acounter substrate (sealing substrate) of the display panel 8006 can havea touch sensor function. A photosensor may be provided in each pixel ofthe display panel 8006 so that an optical touch sensor is obtained.

The frame 8009 protects the display panel 8006 and also serves as anelectromagnetic shield for blocking electromagnetic waves generated bythe operation of the printed board 8010. The frame 8009 may serve as aradiator plate.

The printed board 8010 has a power supply circuit and a signalprocessing circuit for outputting a video signal and a clock signal. Asa power source for supplying power to the power supply circuit, anexternal commercial power source or the battery 8011 provided separatelymay be used. The battery 8011 can be omitted in the case of using acommercial power source.

The display module 8000 can be additionally provided with a member suchas a polarizing plate, a retardation plate, or a prism sheet.

FIGS. 26A to 26G illustrate electronic devices. These electronic devicescan include a housing 9000, a display portion 9001, a speaker 9003,operation keys 9005, a connection terminal 9006, a sensor 9007, amicrophone 9008, and the like.

The electronic devices illustrated in FIGS. 26A to 26G can have avariety of functions, for example, a function of displaying a variety ofdata (a still image, a moving image, a text image, and the like) on thedisplay portion, a touch sensor function, a function of displaying acalendar, date, time, and the like, a function of controlling a processwith a variety of software (programs), a wireless communicationfunction, a function of being connected to a variety of computernetworks with a wireless communication function, a function oftransmitting and receiving a variety of data with a wirelesscommunication function, a function of reading a program or data storedin a memory medium and displaying the program or data on the displayportion, and the like. Note that functions that can be provided for theelectronic devices illustrated in FIGS. 26A to 26G are not limited tothose described above, and the electronic devices can have a variety offunctions. Although not illustrated in FIGS. 26A to 26G, the electronicdevices may include a plurality of display portions. The electronicdevices may have a camera or the like and a function of taking a stillimage, a function of taking a moving image, a function of storing thetaken image in a memory medium (an external memory medium or a memorymedium incorporated in the camera), a function of displaying the takenimage on the display portion, or the like.

The electronic devices illustrated in FIGS. 26A to 26G are described indetail below.

FIG. 26A is a perspective view of a portable information terminal 9100.The display portion 9001 of the portable information terminal 9100 isflexible. Therefore, the display portion 9001 can be incorporated alonga bent surface of a bent housing 9000. In addition, the display portion9001 includes a touch sensor, and operation can be performed by touchingthe screen with a finger, a stylus, or the like. For example, when anicon displayed on the display portion 9001 is touched, an applicationcan be started.

FIG. 26B is a perspective view of a portable information terminal 9101.The portable information terminal 9101 functions as, for example, one ormore of a telephone set, a notebook, and an information browsing system.Specifically, the portable information terminal can be used as asmartphone. Note that the speaker 9003, the connection terminal 9006,the sensor 9007, and the like, which are not shown in FIG. 26B, can bepositioned in the portable information terminal 9101 as in the portableinformation terminal 9100 shown in FIG. 26A. The portable informationterminal 9101 can display characters and image information on itsplurality of surfaces. For example, three operation buttons 9050 (alsoreferred to as operation icons, or simply, icons) can be displayed onone surface of the display portion 9001. Furthermore, information 9051indicated by dashed rectangles can be displayed on another surface ofthe display portion 9001. Examples of the information 9051 includedisplay indicating reception of an incoming email, social networkingservice (SNS) message, call, and the like; the title and sender of anemail and SNS message; the date; the time; remaining battery; and thereception strength of an antenna. Instead of the information 9051, theoperation buttons 9050 or the like may be displayed on the positionwhere the information 9051 is displayed.

FIG. 26C is a perspective view of a portable information terminal 9102.The portable information terminal 9102 has a function of displayinginformation on three or more surfaces of the display portion 9001. Here,information 9052, information 9053, and information 9054 are displayedon different surfaces. For example, a user of the portable informationterminal 9102 can see the display (here, the information 9053) with theportable information terminal 9102 put in a breast pocket of his/herclothes. Specifically, a caller's phone number, name, or the like of anincoming call is displayed in a position that can be seen from above theportable information terminal 9102. Thus, the user can see the displaywithout taking out the portable information terminal 9102 from thepocket and decide whether to answer the call.

FIG. 26D is a perspective view of a watch-type portable informationterminal 9200. The portable information terminal 9200 is capable ofexecuting a variety of applications such as mobile phone calls,e-mailing, viewing and editing texts, music reproduction, Internetcommunication, and computer games. The display surface of the displayportion 9001 is bent, and images can be displayed on the bent displaysurface. The portable information terminal 9200 can employshort-distance wireless communication that is a communication methodbased on an existing communication standard. In that case, for example,mutual communication between the portable information terminal 9200 anda headset capable of wireless communication can be performed, and thushands-free calling is possible. The portable information terminal 9200includes the connection terminal 9006, and data can be directlytransmitted to and received from another information terminal via aconnector. Power charging through the connection terminal 9006 ispossible. Note that the charging operation may be performed by wirelesspower feeding without using the connection terminal 9006.

FIGS. 26E, 26F, and 26G are perspective views of a foldable portableinformation terminal 9201. FIG. 26E is a perspective view illustratingthe portable information terminal 9201 that is opened. FIG. 26F is aperspective view illustrating the portable information terminal 9201that is being opened or being folded. FIG. 26G is a perspective viewillustrating the portable information terminal 9201 that is folded. Theportable information terminal 9201 is highly portable when folded. Whenthe portable information terminal 9201 is opened, a seamless largedisplay region is highly browsable. The display portion 9001 of theportable information terminal 9201 is supported by three housings 9000joined together by hinges 9055. By folding the portable informationterminal 9201 at a connection portion between two housings 9000 with thehinges 9055, the portable information terminal 9201 can be reversiblychanged in shape from an opened state to a folded state. For example,the portable information terminal 9201 can be bent with a radius ofcurvature of greater than or equal to 1 mm and less than or equal to 150mm.

The electronic devices described in this embodiment each include thedisplay portion for displaying some sort of data. Note that thelight-emitting device of one embodiment of the present invention canalso be used for an electronic device which does not have a displayportion. The structure in which the display portion of the electronicdevice described in this embodiment is flexible and display can beperformed on the bent display surface or the structure in which thedisplay portion of the electronic device is foldable is described as anexample; however, the structure is not limited thereto and a structurein which the display portion of the electronic device is inflexible anddisplay is performed on a plane portion may be employed.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 5

In this embodiment, the light-emitting device of one embodiment of thepresent invention will be described with reference to FIGS. 27A to 27C.

FIG. 27A is a perspective view of a light-emitting device 3000 shown inthis embodiment, and FIG. 27B is a cross-sectional view alongdashed-dotted line E-F in FIG. 27A. Note that in FIG. 27A, somecomponents are illustrated by broken lines in order to avoid complexityof the drawing.

The light-emitting device 3000 illustrated in FIGS. 27A and 27B includesa substrate 3001, a light-emitting element 3005 over the substrate 3001,a first sealing region 3007 provided around the light-emitting element3005, and a second sealing region 3009 provided around the first sealingregion 3007.

Light is emitted from the light-emitting element 3005 through one orboth of the substrate 3001 and a substrate 3003. In FIGS. 27A and 27B, astructure in which light is emitted from the light-emitting element 3005to the lower side (the substrate 3001 side) is illustrated.

As illustrated in FIGS. 27A and 27B, the light-emitting device 3000 hasa double sealing structure in which the light-emitting element 3005 issurrounded by the first sealing region 3007 and the second sealingregion 3009. With the double sealing structure, entry of impurities(e.g., water, oxygen, and the like) from the outside into thelight-emitting element 3005 can be preferably suppressed. Note that itis not necessary to provide both the first sealing region 3007 and thesecond sealing region 3009. For example, only the first sealing region3007 may be provided.

Note that in FIG. 27B, the first sealing region 3007 and the secondsealing region 3009 are each provided in contact with the substrate 3001and the substrate 3003. However, without limitation to such a structure,for example, one or both of the first sealing region 3007 and the secondsealing region 3009 may be provided in contact with an insulating filmor a conductive film provided on the substrate 3001. Alternatively, oneor both of the first sealing region 3007 and the second sealing region3009 may be provided in contact with an insulating film or a conductivefilm provided on the substrate 3003.

The substrate 3001 and the substrate 3003 can have structures similar tothose of the substrate 102 and the substrate 152 described in Embodiment1, respectively. The light-emitting element 3005 can have a structuresimilar to that of any of the first to third light-emitting elementsdescribed in Embodiment 1.

For the first sealing region 3007, a material containing glass (e.g., aglass fit, a glass ribbon, and the like) can be used. For the secondsealing region 3009, a material containing a resin can be used. With theuse of the material containing glass for the first sealing region 3007,productivity and a sealing property can be improved. Moreover, with theuse of the material containing a resin for the second sealing region3009, impact resistance and heat resistance can be improved. However,the materials used for the first sealing region 3007 and the secondsealing region 3009 are not limited to such, and the first sealingregion 3007 may be formed using the material containing a resin and thesecond sealing region 3009 may be formed using the material containingglass.

The glass frit may contain, for example, magnesium oxide, calcium oxide,strontium oxide, barium oxide, cesium oxide, sodium oxide, potassiumoxide, boron oxide, vanadium oxide, zinc oxide, tellurium oxide,aluminum oxide, silicon dioxide, lead oxide, tin oxide, phosphorusoxide, ruthenium oxide, rhodium oxide, iron oxide, copper oxide,manganese dioxide, molybdenum oxide, niobium oxide, titanium oxide,tungsten oxide, bismuth oxide, zirconium oxide, lithium oxide, antimonyoxide, lead borate glass, tin phosphate glass, vanadate glass, orborosilicate glass. The glass frit preferably contains at least one kindof transition metal to absorb infrared light.

As the above glass frits, for example, a fit paste is applied to asubstrate and is subjected to heat treatment, laser light irradiation,or the like. The frit paste contains the glass frit and a resin (alsoreferred to as a binder) diluted by an organic solvent. Note that anabsorber which absorbs light having the wavelength of laser light may beadded to the glass frit. For example, an Nd:YAG laser or a semiconductorlaser is preferably used as the laser. The shape of laser light may becircular or quadrangular.

As the above material containing a resin, for example, materials thatinclude polyester, polyolefin, polyamide (e.g., nylon or aramid),polyimide, polycarbonate, polyurethane, an acrylic resin, an epoxyresin, or a resin having a siloxane bond can be used.

Note that in the case where the material containing glass is used forone or both of the first sealing region 3007 and the second sealingregion 3009, the material containing glass preferably has a thermalexpansion coefficient close to that of the substrate 3001. With theabove structure, generation of a crack in the material containing glassor the substrate 3001 due to thermal stress can be suppressed.

For example, the following advantageous effect can be obtained in thecase where the material containing glass is used for the first sealingregion 3007 and the material containing a resin is used for the secondsealing region 3009.

The second sealing region 3009 is provided closer to an outer portion ofthe light-emitting device 3000 than the first sealing region 3007 is. Inthe light-emitting device 3000, distortion due to external force or thelike increases toward the outer portion. Thus, the outer portion of thelight-emitting device 3000 where a larger amount of distortion isgenerated, that is, the second sealing region 3009 is sealed using thematerial containing a resin and the first sealing region 3007 providedon an inner side of the second region 3009 is sealed using the materialcontaining glass, whereby the light-emitting device 3000 is less likelyto be damaged even when distortion due to external force or the like isgenerated.

Furthermore, as illustrated in FIG. 27B, a first region 3011 correspondsto the region surrounded by the substrate 3001, the substrate 3003, thefirst sealing region 3007, and the second sealing region 3009. A secondregion 3013 corresponds to the region surrounded by the substrate 3001,the substrate 3003, the light-emitting element 3005, and the firstsealing region 3007.

The first region 3011 and the second region 3013 are preferably filledwith, for example, an inert gas such as a rare gas or a nitrogen gas.Note that for the first region 3011 and the second region 3013, areduced pressure state is preferred to an atmospheric pressure state.

FIG. 27C illustrates a modification example of the structure in FIG.27B. FIG. 27C is a cross-sectional view illustrating the modificationexample of the light-emitting device 3000.

FIG. 27C illustrates a structure in which a desiccant 3018 is providedin a recessed portion provided in part of the substrate 3003. The othercomponents are the same as those of the structure illustrated in FIG.27B.

As the desiccant 3018, a substance which adsorbs moisture and the likeby chemical adsorption or a substance which adsorbs moisture and thelike by physical adsorption can be used. Examples of the substance thatcan be used as the desiccant 3018 include alkali metal oxides, alkalineearth metal oxide (e.g., calcium oxide, barium oxide, and the like),sulfate, metal halides, perchlorate, zeolite, silica gel, and the like.

Next, modification examples of the light-emitting device 3000 which isillustrated in FIG. 27B are described with reference to FIGS. 28A to28D. Note that FIGS. 28A to 28D are cross-sectional views illustratingthe modification examples of the light-emitting device 3000 illustratedin FIG. 27B.

In the light-emitting device illustrated in FIG. 28A, the second sealingregion 3009 is not provided but only the first sealing region 3007 isprovided. Moreover, in the light-emitting device illustrated in FIG.28A, a region 3014 is provided instead of the second region 3013illustrated in FIG. 27B.

For the region 3014, for example, materials that include polyester,polyolefin, polyamide (e.g., nylon or aramid), polyimide, polycarbonate,polyurethane, an acrylic resin, an epoxy resin, or a resin having asiloxane bond can be used.

When the above-described material is used for the region 3014, what iscalled a solid-sealing light-emitting device can be obtained.

In the light-emitting device illustrated in FIG. 28B, a substrate 3015is provided on the substrate 3001 side of the light-emitting deviceillustrated in FIG. 28A.

The substrate 3015 has unevenness as illustrated in FIG. 28B. With astructure in which the substrate 3015 having unevenness is provided onthe side through which light emitted from the light-emitting element3005 is extracted, the efficiency of extraction of light from thelight-emitting element 3005 can be improved. Note that instead of thestructure having unevenness and illustrated in FIG. 28B, a substratehaving a function as a diffusion plate may be provided.

In the light-emitting device illustrated in FIG. 28C, light is extractedthrough the substrate 3003 side, unlike in the light-emitting deviceillustrated in FIG. 28A, in which light is extracted through thesubstrate 3001 side.

The light-emitting device illustrated in FIG. 28C includes the substrate3015 on the substrate 3003 side. The other components are the same asthose of the light-emitting device illustrated in FIG. 28B.

In the light-emitting device illustrated in FIG. 28D, the substrate 3003and the substrate 3015 included in the light-emitting device illustratedin FIG. 28C are not provided but a substrate 3016 is provided.

The substrate 3016 includes first unevenness positioned closer to thelight-emitting element 3005 and second unevenness positioned fartherfrom the light-emitting element 3005. With the structure illustrated inFIG. 28D, the efficiency of extraction of light from the light-emittingelement 3005 can be further improved.

Thus, the use of the structure described in this embodiment can obtain alight-emitting device in which deterioration of a light-emitting elementdue to impurities such as moisture and oxygen is suppressed.Alternatively, with the structure described in this embodiment, alight-emitting device having high light extraction efficiency can beobtained.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

Embodiment 6

In this embodiment, examples in which the light-emitting device of oneembodiment of the present invention is applied to various lightingdevices and electronic devices will be described with reference to FIGS.29A to 29C.

An electronic device or a lighting device that has a light-emittingregion with a curved surface can be obtained with the use of thelight-emitting device of one embodiment of the present invention whichis manufactured over a substrate having flexibility.

Furthermore, a light-emitting device to which one embodiment of thepresent invention is applied can also be applied to lighting for motorvehicles, examples of which are lighting for a dashboard, a windshield,a ceiling, and the like.

FIG. 29A is a perspective view illustrating one surface of amultifunction terminal 3500, and FIG. 29B is a perspective viewillustrating the other surface of the multifunction terminal 3500. In ahousing 3502 of the multifunction terminal 3500, a display portion 3504,a camera 3506, lighting 3508, and the like are incorporated. Thelight-emitting device of one embodiment of the present invention can beused for the lighting 3508.

The lighting 3508 that includes the light-emitting device of oneembodiment of the present invention functions as a planar light source.Thus, unlike a point light source typified by an LED, the lighting 3508can provide light emission with low directivity. When the lighting 3508and the camera 3506 are used in combination, for example, imaging can beperformed by the camera 3506 with the lighting 3508 lighting orflashing. Because the lighting 3508 functions as a planar light source,a photograph as if taken under natural light can be taken.

Note that the multifunction terminal 3500 illustrated in FIGS. 29A and29B can have a variety of functions as in the electronic devicesillustrated in FIGS. 26A to 26G.

The housing 3502 can include a speaker, a sensor (a sensor having afunction of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, odor, or infrared rays), amicrophone, and the like. When a detection device including a sensor fordetecting inclination, such as a gyroscope or an acceleration sensor, isprovided inside the multifunction terminal 3500, display on the screenof the display portion 3504 can be automatically switched by determiningthe orientation of the multifunction terminal 3500 (whether themultifunction terminal is placed horizontally or vertically for alandscape mode or a portrait mode).

The display portion 3504 may function as an image sensor. For example,an image of a palm print, a fingerprint, or the like is taken when thedisplay portion 3504 is touched with the palm or the finger, wherebypersonal authentication can be performed. Furthermore, by providing abacklight or a sensing light source which emits near-infrared light inthe display portion 3504, an image of a finger vein, a palm vein, or thelike can be taken. Note that the light-emitting device of one embodimentof the present invention may be used for the display portion 3504.

FIG. 29C is a perspective view of a security light 3600. The securitylight 3600 includes lighting 3608 on the outside of the housing 3602,and a speaker 3610 and the like are incorporated in the housing 3602.The light-emitting device of one embodiment of the present invention canbe used for the lighting 3608.

The security light 3600 emits light when the lighting 3608 is gripped orheld, for example. An electronic circuit that can control the manner oflight emission from the security light 3600 may be provided in thehousing 3602. The electronic circuit may be a circuit that enables lightemission once or intermittently plural times or may be a circuit thatcan adjust the amount of emitted light by controlling the current valuefor light emission. A circuit with which a loud audible alarm is outputfrom the speaker 3610 at the same time as light emission from thelighting 3608 may be incorporated.

The security light 3600 can emit light in various directions; therefore,it is possible to intimidate a thug or the like with light, or light andsound. Moreover, the security light 3600 may include a camera such as adigital still camera to have a photography function.

As described above, lighting devices and electronic devices can beobtained by application of the light-emitting device of one embodimentof the present invention. Note that the light-emitting device can beused for lighting devices and electronic devices in a variety of fieldswithout being limited to the lighting devices and the electronic devicesdescribed in this embodiment.

The structure described in this embodiment can be combined with any ofthe structures described in the other embodiments as appropriate.

This application is based on Japanese Patent Application serial no.2014-216875 filed with Japan Patent Office on Oct. 24, 2014, the entirecontents of which are hereby incorporated by reference.

1. A light-emitting device comprising: a first light-emitting elementcomprising: a first lower electrode; a first light-emitting layer overthe first lower electrode; a second light-emitting layer over the firstlight-emitting layer; and an upper electrode over the secondlight-emitting layer, and a second light-emitting element comprising: asecond lower electrode; the first light-emitting layer over the secondlower electrode; the second light-emitting layer over the firstlight-emitting layer; and the upper electrode over the secondlight-emitting layer, wherein an emission spectrum of the firstlight-emitting layer peaks at a longer wavelength than an emissionspectrum of the second light-emitting layer, wherein a distance betweenthe first lower electrode and the first light-emitting layer is shorterthan a distance between the second lower electrode and the firstlight-emitting layer, and wherein the emission spectrum of the firstlight-emitting layer has a peak in a yellow wavelength range.
 2. Thelight-emitting device according to claim 1 wherein the emission spectrumof the second light-emitting layer has a peak in any one of a violetwavelength range, a blue wavelength range, and a blue green wavelengthrange.
 3. The light-emitting device according to claim 1, wherein theemission spectrum of the second light-emitting layer has peak in a bluewavelength range.
 4. The light-emitting device according to claim 1,wherein the yellow wavelength range is greater than or equal to 550 nmand less than 600 nm.
 5. The light-emitting device according to claim 1,wherein an optical path length between the first lower electrode and thesecond light-emitting layer is approximately 3λ_(B)/4 (λ_(B) representsa wavelength of blue light), and wherein an optical path length betweenthe second lower electrode and the first light-emitting layer isapproximately 3λ_(Y)/4 (λ_(Y) represents a wavelength of yellow light).6. The light-emitting device according to claim 1, wherein the firstlower electrode and the second lower electrode each comprise silver. 7.The light-emitting device according to claim 1, wherein the firstlight-emitting layer comprise s a phosphorescent material, and whereinthe second light-emitting layer comprise s a fluorescent material.
 8. Anelectronic device comprising: the light-emitting device according toclaim 1; and a housing or a touch sensor.
 9. A lighting devicecomprising: the light-emitting device according to claim 1; and ahousing.
 10. A light-emitting device comprising: a first light-emittingelement comprising: a first lower electrode; a first transparentconductive layer over the first lower electrode; a first light-emittinglayer over the first transparent conductive layer; a charge-generationlayer over the first light-emitting layer; a second light-emitting layerover the charge-generation layer; and an upper electrode over the secondlight-emitting layer, a second light-emitting element comprising: asecond lower electrode; a second transparent conductive layer over thesecond lower electrode; the first light-emitting layer over the secondtransparent conductive layer; the charge-generation layer over the firstlight-emitting layer; the second light-emitting layer over thecharge-generation layer; and the upper electrode over the secondlight-emitting layer, and a third light-emitting element comprising: athird lower electrode; a third transparent conductive layer over thethird lower electrode; the first light-emitting layer over the thirdtransparent conductive layer; the charge-generation layer over the firstlight-emitting layer; the second light-emitting layer over thecharge-generation layer; and the upper electrode over the secondlight-emitting layer, wherein light emitted from the firstlight-emitting element has at least one peak in a wavelength range ofgreater than or equal to 400 nm and less than 480 nm, wherein lightemitted from the second light-emitting element has at least one peak ina wavelength range of greater than or equal to 480 nm and less than 600nm, and wherein light emitted from the third light-emitting element hasat least one peak in a wavelength range of greater than or equal to 600nm and less than or equal to 740 nm.
 11. The light-emitting deviceaccording to claim 10, wherein the first lower electrode, the secondlower electrode, and the third lower electrode each comprise silver. 12.The light-emitting device according to claim 10, wherein the firstlight-emitting layer comprise s a phosphorescent material, and whereinthe second light-emitting layer comprise s a fluorescent material. 13.An electronic device comprising: the light-emitting device according toclaim 10; and a housing or a touch sensor.
 14. A lighting devicecomprising: the light-emitting device according to claim 10; and ahousing. 15-19. (canceled)